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73-411: Four general filter functions are desirable: In general, most RF and microwave filters are most often made up of one or more coupled resonators , and thus any technology that can be used to make resonators can also be used to make filters. The unloaded quality factor of the resonators being used will generally set the selectivity the filter can achieve. The book by Matthaei, Young and Jones provides

146-463: A Bragg reflector ) typically consists of an odd total number of materials with alternating layers of high and low acoustic impedance materials. The thickness of the mirror materials must also be optimized to be the quarter wavelength for maximum acoustic reflectivity. The basic principle of the SMR structure was introduced in 1965. Schematic pictures of thin film resonators show only the basic principles of

219-445: A harmonic oscillator . Systems with one degree of freedom, such as a mass on a spring, pendulums , balance wheels , and LC tuned circuits have one resonant frequency. Systems with two degrees of freedom, such as coupled pendulums and resonant transformers can have two resonant frequencies. A crystal lattice composed of N atoms bound together can have N resonant frequencies. As the number of coupled harmonic oscillators grows,

292-547: A laser , light is amplified in a cavity resonator that is usually composed of two or more mirrors. Thus an optical cavity , also known as a resonator, is a cavity with walls that reflect electromagnetic waves (i.e. light ). This allows standing wave modes to exist with little loss. Mechanical resonators are used in electronic circuits to generate signals of a precise frequency . For example, piezoelectric resonators , commonly made from quartz , are used as frequency references. Common designs consist of electrodes attached to

365-409: A piezoelectric material manufactured by thin film methods between two conductive – typically metallic – electrodes and acoustically isolated from the surrounding medium. The operation is based on the piezoelectricity of the piezolayer between the electrodes. FBAR devices using piezoelectric films with thicknesses typically ranging from several micrometres down to tenths of micrometres resonate in

438-507: A short circuit or open circuit, connected in series or parallel with a main transmission line. Planar transmission-line resonators are commonly employed for coplanar , stripline , and microstrip transmission lines. Such planar transmission-line resonators can be very compact in size and are widely used elements in microwave circuitry. In cryogenic solid-state research, superconducting transmission-line resonators contribute to solid-state spectroscopy and quantum information science. In

511-566: A coil of wire, is self-resonant at a certain frequency due to the parasitic capacitance between its turns. This is often an unwanted effect that can cause parasitic oscillations in RF circuits. The self-resonance of inductors is used in a few circuits, such as the Tesla coil . A cavity resonator is a hollow closed conductor such as a metal box or a cavity within a metal block, containing electromagnetic waves (radio waves) reflecting back and forth between

584-748: A crystal/crystals in applications where frequencies more than 100 MHz and/or very low jitter is one of the performance targets. FBARs can also be used as sensors. For instance, when a FBAR device is put under mechanical pressure its resonance frequency will shift. Sensing of humidity and volatile organic compounds (VOCs) are demonstrated by using FBARs. A tactile sensor array may also consist of FBAR devices, and gravimetric or mass sensing can be based on FBAR resonators. As discrete components FBAR technology based parts like basic resonators and filters are packaged in miniaturised/small form factor like wafer level packages . FBARs can also be integrated with power amplifiers (PA) or low noise amplifiers (LNA) to form

657-420: A free-standing resonator structure air is used to separate the resonator from the substrate/surrounding. The structure of a free-standing resonator is based on some typical manufacturing steps used in micro-electromechanical systems MEMS . In an SMR structure acoustic mirror(s) providing an acoustic isolation is constructed between the resonator and the surrounding like the substrate. The acoustic mirror (such as

730-426: A good reference to the design and realization of RF and microwave filters. Generalized filter theory operates with resonant frequencies and coupling coefficients of coupled resonators in a microwave filter. The simplest resonator structure that can be used in rf and microwave filters is an LC tank circuit consisting of parallel or series inductors and capacitors. These have the advantage of being very compact, but

803-421: A lowest frequency called the fundamental frequency . The above analysis assumes the medium inside the resonator is homogeneous, so the waves travel at a constant speed, and that the shape of the resonator is rectilinear. If the resonator is inhomogeneous or has a nonrectilinear shape, like a circular drumhead or a cylindrical microwave cavity , the resonant frequencies may not occur at equally spaced multiples of

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876-447: A module solution with the related electronic circuitry. Although monolithic integrated of FBARs on the same substrate with the electronic circuitry like CMOS has been demonstrated it requires several additional process steps and mask layers on top of IC technology increasing the cost of the solution. Therefore, monolithic solutions have not been progressed as much as module solutions in commercial applications. Typical module solutions are

949-528: A network of resonators (either in half- ladder , full-ladder, lattice , a combination of lattice and ladder or stacked topologies) and are designed to remove unwanted frequencies from being transmitted in such devices, while allowing other specific frequencies to be received and transmitted. FBAR filters can also be found in duplexers . FBAR filter technology is complementing surface acoustic wave (SAW) filter technology in areas where increased power handling capability, and electrostatic discharge (ESD) tolerance

1022-402: A particular engine speed or range of speeds. In many keyboard percussion instruments, below the centre of each note is a tube, which is an acoustic cavity resonator . The length of the tube varies according to the pitch of the note, with higher notes having shorter resonators. The tube is open at the top end and closed at the bottom end, creating a column of air that resonates when the note

1095-407: A piece of quartz, in the shape of a rectangular plate for high frequency applications, or in the shape of a tuning fork for low frequency applications. The high dimensional stability and low temperature coefficient of quartz helps keeps resonant frequency constant. In addition, the quartz's piezoelectric property converts the mechanical vibrations into an oscillating voltage , which is picked up by

1168-589: A power amplifier- duplexer module (PAD), or a low-noise amplifier (LNA)-filter module where FBAR(s) and the related circuitry are packaged in the same package possibly on a separate module substrate. FBARs can be integrated in complex communication like SimpleLink modules for avoiding area/space requirements of an external, packaged crystal. Therefore, FBAR technology has a key role in electronics miniaturisation specifically in applications where oscillators and precise high performance filters are needed. The use of thin film piezoelectric materials in electronics began in

1241-631: A project on FBARs in 1993 concentrating in free-standing resonators and filters. In 1999 FBAR activity became part of Agilent Technologies Inc., which in 2001 delivered 25,000 FBAR duplexers for N-CDMA phones. Later in 2005, FBAR activity at Agilent was one of the technologies of Avago Technologies Ltd., which acquired Broadcom Corporation in 2015. In 2016 Avago Technologies Ltd. changed its name to Broadcom Inc. , currently active in providing FBAR-based products. Infineon Technologies AG started to work with SMR-FBARs in 1999, concentrating in telecommunication filters for mobile applications. The first product

1314-477: A resonator can be either electromagnetic or mechanical (including acoustic ). Resonators are used to either generate waves of specific frequencies or to select specific frequencies from a signal. Musical instruments use acoustic resonators that produce sound waves of specific tones. Another example is quartz crystals used in electronic devices such as radio transmitters and quartz watches to produce oscillations of very precise frequency. A cavity resonator

1387-453: A specific resistor component, or due to resistance of the inductor windings. Such resonant circuits are also called RLC circuits after the circuit symbols for the components. A distributed-parameter resonator has capacitance, inductance, and resistance that cannot be isolated into separate lumped capacitors, inductors, or resistors. An example of this, much used in filtering , is the helical resonator . An inductor consisting of

1460-505: A thin film depends on the piezomaterial selected and many other items like the surface on which the film is grown and various manufacturing - thin film growth - conditions (temperatures selected, pressure, gases used, vacuum conditions etc.). Any material like lead zirconate titanate (PZT) or barium strontium titanate (BST) from the list of piezoelectric materials could act as an active material in an FBAR. However two compound materials aluminium nitride (AlN) and zinc oxide (ZnO) are

1533-401: A transmission line causes reflection of the transmitted signal. Two such reflectors on a transmission line evoke standing waves between them and thus act as a one-dimensional resonator, with the resonance frequencies determined by their distance and the effective dielectric constant of the transmission line. A common form is the resonant stub , a length of transmission line terminated in either

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1606-476: A wider band gap has become the most used material in industrial applications, which require a wide bandwidth in signal processing. Compatibility with the silicon integrated circuit technology has supported AlN in FBAR resonator based products like radio frequency filters, duplexers, RF power amplifier or RF receiver modules. Thin film piezoelectric sensors may be based on various piezoelectric materials depending on

1679-522: Is a developing area for FBAR resonators and structures based on them. Targets to measure and also possibly control small amount of materials/liquids/gas, and replacing crystal(s) as miniaturized in various sensing and actuation tasks like in micro mirror displays (DMD)s are under research and development as well as energy harvesting by utilizing nanogenerators . As of 2022 there are two known structures for thin-film bulk acoustic wave (BAW) resonators: free-standing and solidly mounted (SMR) resonators. In

1752-588: Is an example. These are the new class of highly tunable microwave filters. These special kinds of filters can be implemented on waveguides, SIW or on low-cost PCB technology and can be tuned to any lower or higher frequency with the help of switches inserted at appropriate positions to achieve a broad tuning range. Resonators A resonator is a device or system that exhibits resonance or resonant behavior. That is, it naturally oscillates with greater amplitude at some frequencies , called resonant frequencies , than at other frequencies. The oscillations in

1825-461: Is equal to an integer number of wavelengths λ {\displaystyle \lambda \,} of the wave: If the velocity of a wave is c {\displaystyle c\,} , the frequency is f = c / λ {\displaystyle f=c/\lambda \,} so the resonant frequencies are: So the resonant frequencies of resonators, called normal modes , are equally spaced multiples ( harmonics ) of

1898-482: Is made by cutting a narrow slit along the length of a conducting tube. The slit has an effective capacitance and the bore of the resonator has an effective inductance. Therefore, the LGR can be modeled as an RLC circuit and has a resonant frequency that is typically between 200 MHz and 2 GHz. In the absence of radiation losses, the effective resistance of the LGR is determined by the resistivity and electromagnetic skin depth of

1971-528: Is needed. Frequencies more than 1.5–2.5 GHz are well-suited for FBAR devices. FBARs on a silicon substrate can be manufactured in high volumes and the manufacturing is supported by all development of semiconductor device fabrication methods. Future requirements of new applications like filtering bandwidth with steep stopband attenuation and lowest possible insertion loss have effects on resonator performance and show development steps needed. FBARs can also be used in oscillators and synchronizers to replace

2044-572: Is one in which waves exist in a hollow space inside the device. In electronics and radio, microwave cavities consisting of hollow metal boxes are used in microwave transmitters, receivers and test equipment to control frequency, in place of the tuned circuits which are used at lower frequencies. Acoustic cavity resonators, in which sound is produced by air vibrating in a cavity with one opening, are known as Helmholtz resonators . A physical system can have as many resonant frequencies as it has degrees of freedom ; each degree of freedom can vibrate as

2117-455: Is required. The coaxial resonators may make use of high-dielectric constant materials to reduce their overall size. Still widely used in the 40 MHz to 960 MHz frequency range, well constructed cavity filters are capable of high selectivity even under power loads of at least a megawatt. Higher Q quality factor , as well as increased performance stability at closely spaced (down to 75 kHz) frequencies, can be achieved by increasing

2190-514: Is struck. This adds depth and volume to the note. In string instruments, the body of the instrument is a resonator. The tremolo effect of a vibraphone is achieved via a mechanism that opens and shuts the resonators. String instruments such as the bluegrass banjo may also have resonators. Many five-string banjos have removable resonators, so players can use the instrument with a resonator in bluegrass style, or without it in folk music style. The term resonator , used by itself, may also refer to

2263-421: Is surrounded by a material with much lower dielectric constant, then this abrupt change in dielectric constant can cause confinement of an electromagnetic wave, which leads to a resonator that acts similarly to a cavity resonator. Transmission lines are structures that allow broadband transmission of electromagnetic waves, e.g. at radio or microwave frequencies. Abrupt change of impedance (e.g. open or short) in

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2336-516: Is very similar to the processes used to manufacture printed circuit boards and these filters have the advantage of largely being planar. Precision planar filters are manufactured using a thin-film process. Higher Q factors can be obtained by using low loss tangent dielectric materials for the substrate such as quartz or sapphire and lower resistance metals such as gold. Coaxial transmission lines provide higher quality factor than planar transmission lines, and are thus used when higher performance

2409-409: The standing wave is imposed on the beam. This type of system can be used as a sensor to track changes in frequency or phase of the resonance of the fiber. One application is as a measurement device for dimensional metrology . The most familiar examples of acoustic resonators are in musical instruments . Every musical instrument has resonators. Some generate the sound directly, such as

2482-423: The muffler to reduce noise, by making sound waves "cancel each other out". The "exhaust note" is an important feature for some vehicle owners, so both the original manufacturers and the after-market suppliers use the resonator to enhance the sound. In " tuned exhaust " systems designed for performance, the resonance of the exhaust pipes can also be used to remove combustion products from the combustion chamber at

2555-413: The resonator guitar . The modern ten-string guitar , invented by Narciso Yepes , adds four sympathetic string resonators to the traditional classical guitar. By tuning these resonators in a very specific way (C, B♭, A♭, G♭) and making use of their strongest partials (corresponding to the octaves and fifths of the strings' fundamental tones), the bass strings of the guitar now resonate equally with any of

2628-406: The 12 tones of the chromatic octave. The guitar resonator is a device for driving guitar string harmonics by an electromagnetic field. This resonance effect is caused by a feedback loop and is applied to drive the fundamental tones, octaves, 5th, 3rd to an infinite sustain . Thin-film bulk acoustic resonator A thin-film bulk acoustic resonator (FBAR or TFBAR) is a device consisting of

2701-510: The 600 MHz and higher range, the inductors in the tank circuit become too small to be practical. Since the electrical reactance of an inductor of a certain inductance increases linearly with respect to frequency, at higher frequencies, to achieve the same reactance, a prohibitively low inductance may be required. Planar transmission lines , such as microstrip , coplanar waveguide and stripline , can also make good resonators and filters. The processes used to manufacture microstrip circuits

2774-549: The antenna/antenna system. Trends to utilize RF spectrum more efficiently with higher frequencies than roughly 1.5–2.5 GHz and in some cases also simultaneously with increasing RF output power have supported FBAR technology to become one of the key enabling technologies in telecommunication realisations. FBAR technology complements and in some cases competes with surface acoustic wave (SAW) technology and FBAR resonators can replace crystals in crystal oscillators and crystal filters at frequencies more than 100 MHz. Sensory

2847-405: The application, but two compound piezoelectric materials are favored due to simplicity of manufacturing. Doping or adding new materials like scandium (Sc) , are new directions to improve material properties of AlN for FBARs. Research of new electrode materials or alternative materials to aluminium like by replacing one of the metal electrodes with very light materials like graphene for minimising

2920-417: The attached electrodes. These crystal oscillators are used in quartz clocks and watches, to create the clock signal that runs computers, and to stabilize the output signal from radio transmitters . Mechanical resonators can also be used to induce a standing wave in other media. For example, a multiple degree of freedom system can be created by imposing a base excitation on a cantilever beam. In this case

2993-404: The beam after passing through the resonators. The first resonator causes bunching of the particles passing through it. The bunched particles travel in a field-free region where further bunching occurs, then the bunched particles enter the second resonator giving up their energy to excite it into oscillations. It is a particle accelerator that works in conjunction with a specifically tuned cavity by

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3066-475: The cavity is conveniently small in size. Due to the low resistance of their conductive walls, cavity resonators have very high Q factors ; that is their bandwidth , the range of frequencies around the resonant frequency at which they will resonate, is very narrow. Thus they can act as narrow bandpass filters . Cavity resonators are widely used as the frequency determining element in microwave oscillators . Their resonant frequency can be tuned by moving one of

3139-467: The cavity's walls. When a source of radio waves at one of the cavity's resonant frequencies is applied, the oppositely-moving waves form standing waves , and the cavity stores electromagnetic energy. Since the cavity's lowest resonant frequency, the fundamental frequency, is that at which the width of the cavity is equal to a half-wavelength (λ/2), cavity resonators are only used at microwave frequencies and above, where wavelengths are short enough that

3212-428: The coaxial resonators, high-dielectric constant materials may be used to reduce the overall size of the filter. With low-loss dielectric materials, these can offer significantly higher performance than the other technologies previously discussed. Electroacoustic resonators based on piezoelectric materials can be used for filters. Since acoustic wavelength at a given frequency is several orders of magnitude shorter than

3285-439: The conductor used to make the resonator. One key advantage of the LGR is that, at its resonant frequency, its dimensions are small compared to the free-space wavelength of the electromagnetic fields. Therefore, it is possible to use LGRs to construct a compact and high-Q resonator that operates at relatively low frequencies where cavity resonators would be impractically large. If a piece of material with large dielectric constant

3358-412: The configuration of the structures. The reflex klystron is a klystron utilizing only a single apertured cavity resonator through which the beam of charged particles passes, first in one direction. A repeller electrode is provided to repel (or redirect) the beam after passage through the resonator back through the resonator in the other direction and in proper phase to reinforce the oscillations set up in

3431-474: The crystal and increase resonance frequency. FBAR devices can be used for radio frequency filtering, for enabling thin audio speakers and in various sensors. Most smartphones in 2020 include at least one FBAR-based duplexer or filter and some 4/ 5G products may even include 20–30 functionalities based on FBAR technology mainly due to the increased complexity of radio frequency front end (RFFE, RF front end ) electronics – both receiver and transmitter paths – and

3504-442: The distance between the sides is d {\displaystyle d\,} , the length of a round trip is 2 d {\displaystyle 2d\,} . To cause resonance, the phase of a sinusoidal wave after a round trip must be equal to the initial phase so the waves self-reinforce. The condition for resonance in a resonator is that the round trip distance, 2 d {\displaystyle 2d\,} ,

3577-540: The early 1960s at Bell Telephone Laboratories/Bell Labs. Earlier piezoelectric crystals were developed and used as resonators in applications like oscillators with frequencies up to 100 MHz. Thinning was applied for increasing the resonance frequency of the crystals. However, there were limitations of the thinning of crystals and new methods of thin film manufacturing were applied in the early 1970s for increasing accuracy of resonance frequency and targeting increasing manufacturing volumes. TFR Technologies Inc., founded in 1989,

3650-624: The electrical wavelength, electroacoustic resonators are generally smaller by size and weight than electromagnetic counterparts such as cavity resonators. A common example of an electroacoustic resonator is the quartz resonator which essentially is a cut of a piezoelectric quartz crystal clamped by a pair of electrodes. This technology is limited to some tens of megahertz. For microwave frequencies, typically more than 100 MHz, most filters are using thin film technologies such as surface acoustic wave (SAW) and, thin-film bulk acoustic resonator (FBAR, TFBAR) based structures. The waffle-iron filter

3723-410: The extracted RF energy to the load, which may be a cooking chamber in a microwave oven or a high gain antenna in the case of radar. The klystron , tube waveguide, is a beam tube including at least two apertured cavity resonators. The beam of charged particles passes through the apertures of the resonators, often tunable wave reflection grids, in succession. A collector electrode is provided to intercept

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3796-526: The film crystal structure is 41º tilted. It is also possible – depending on the crystal structure of the film – that both waves (L & S) are excited. Therefore, the understanding and control of the crystal structure of the manufactured piezoelectric film is crucial for the operation of the FBAR. For high frequency purposes like filtering of signals the energy conversion efficiency is the most important item and therefore longitudinal (L) waves are favored and targeted to be used. For sensing and actuation purposes

3869-638: The frequency range of 100 MHz to 20 GHz. FBAR or TFBAR resonators fall in the category of bulk acoustic resonators (BAW) and piezoelectric resonators and they are used in applications where high frequency, small size like thickness and/or weight is needed. Industrial application areas of thin film bulk acoustic resonators are ranging from high frequency signal filtering specifically for mobile telecommunication devices, crystal replacements, energy harvesting, acoustic speakers in systems where size matters like hearings aids, as part of mechanical qubits and to sensory. The crystallographic orientation of

3942-490: The functionality of the resonators and for helping to improve the design (layout and cross-sectional structure of the resonator) so as to achieve purity of the resonance and the desired resonance modes. In many applications temperature behavior, stability vs. time, strength and purity of the wanted resonance frequency are forming the base for the performance of the applications based on FBAR resonators. Material choices, layout and design of resonator structures are contributing to

4015-412: The fundamental frequency. They are then called overtones instead of harmonics . There may be several such series of resonant frequencies in a single resonator, corresponding to different modes of vibration. An electrical circuit composed of discrete components can act as a resonator when both an inductor and capacitor are included. Oscillations are limited by the inclusion of resistance, either via

4088-486: The internal volume of the filter cavities. Physical length of conventional cavity filters can vary from over 205 cm in the 40 MHz range, down to under 27.5 cm in the 900 MHz range. In the microwave range (1000 MHz and up), cavity filters become more practical in terms of size and a significantly higher quality factor than lumped element resonators and filters. Pucks made of various dielectric materials can also be used to make resonators. As with

4161-488: The loading of the resonator has been demonstrated to lead better control of the resonance frequency. FBAR resonators can be manufactured on ceramic (Al 2 O 3 or alumina), sapphire , glass or silicon substrates. However silicon wafer is the most common substrate due to its scalability towards mass manufacturing and compatibility with various manufacturing steps needed. During early studies and experimentation phase of thin film resonators in 1967 cadmium sulfide (CdS)

4234-416: The low quality factor of the resonators leads to relatively poor performance. Lumped-Element LC filters have both an upper and lower frequency range. As the frequency gets very low, into the low kHz to Hz range the size of the inductors used in the tank circuit becomes prohibitively large. Very low frequency filters are often designed with crystals to overcome this problem. As the frequency gets higher, into

4307-458: The potential structures. In reality some dielectric layers may be needed for other functions, such as for strengthening various parts of the structure. Additionally if needed – for simplifying the final filter layout in the application – resonator structures can be stacked e.g. built on top of each other, as in certain filter applications. However this approach increases the complexity of manufacturing. Some performance requirements, such as tuning of

4380-402: The resonance frequency, may also require new materials, additional process steps, such as ion milling, which complicates the manufacturing process, and may have affect to system requirements like adding new functionality to produce tuning voltages. The newest approach for developing better performing FBARs is to utilize single crystal AlN instead of polycrystalline AlN, and to place electrodes on

4453-500: The resonator performance and the final performance of the application. Mechanical performance and reliability are determined by the packaging and structure of the resonators in the applications. A common application of FBARs is radio frequency (RF) filters for use in cell phones and other wireless applications like positioning ( GPS , Glonass , BeiDou , Galileo (satellite navigation) etc.), Wi-Fi systems, small telecommunication cells and modules for those. Such filters are made from

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4526-415: The resonator, through which the waves flow, can be viewed as being made of millions of coupled moving parts (such as atoms). Therefore, they can have millions of resonant frequencies, although only a few may be used in practical resonators. The oppositely moving waves interfere with each other, and at its resonant frequencies reinforce each other to create a pattern of standing waves in the resonator. If

4599-557: The resonator. On the beamline of an accelerator system, there are specific sections that are cavity resonators for radio frequency (RF) radiation. The (charged) particles that are to be accelerated pass through these cavities in such a way that the microwave electric field transfers energy to the particles, thus increasing their kinetic energy and thus accelerating them. Several large accelerator facilities employ superconducting niobium cavities for improved performance compared to metallic (copper) cavities. The loop-gap resonator (LGR)

4672-468: The rim of the chamber are cylindrical cavities. The cavities are open along their length and so they connect with the common cavity space. As electrons sweep past these openings they induce a resonant high frequency radio field in the cavity, which in turn causes the electrons to bunch into groups. A portion of this field is extracted with a short antenna that is connected to a waveguide (a metal tube usually of rectangular cross section). The waveguide directs

4745-494: The same side of the piezolayer. In order to realize FBAR structures, many precise simulation steps are required during the design phase in order to predict the purity of the resonance frequency and other performance characteristics. At an early phase of the development, basic finite element method (FEM) based modelling techniques that are used for crystals can also be applied and modified for FBARs. Several new methods, such as scanning laser interferometry, are needed to visualise

4818-404: The structural deformation might be more important than energy conversion efficiency and shear-mode wave excitation will be the target of the manufacturing of the piezoelectric film. Tuneability of resonance frequency of the resonator depends on material choices and may extend application areas. Despite the lower electromechanical coupling coefficient compared to zinc oxide, aluminum nitride, with

4891-420: The time it takes to transfer energy from one to the next becomes significant. The vibrations in them begin to travel through the coupled harmonic oscillators in waves, from one oscillator to the next. The term resonator is most often used for a homogeneous object in which vibrations travel as waves, at an approximately constant velocity, bouncing back and forth between the sides of the resonator. The material of

4964-504: The two most studied piezoelectric materials manufactured for high frequency FBAR realisations. This is due to the fact that the properties like stoichiometry of two compound materials can be easier to control compared to three compound materials manufactured by thin film methods. For example, it is known that thin film ZnO with C axis of the crystal structure (crystalline Z axis) normal to the substrate surface excites longitudinal (L) waves. Shear (transverse) (S) waves are excited if C axis of

5037-441: The walls of the cavity in or out, changing its size. The cavity magnetron is a vacuum tube with a filament in the center of an evacuated, lobed, circular cavity resonator. A perpendicular magnetic field is imposed by a permanent magnet. The magnetic field causes the electrons, attracted to the (relatively) positive outer part of the chamber, to spiral outward in a circular path rather than moving directly to this anode. Spaced about

5110-468: The wooden bars in a xylophone , the head of a drum , the strings in stringed instruments , and the pipes in an organ . Some modify the sound by enhancing particular frequencies, such as the sound box of a guitar or violin . Organ pipes , the bodies of woodwinds , and the sound boxes of stringed instruments are examples of acoustic cavity resonators. The exhaust pipes in automobile exhaust systems are designed as acoustic resonators that work with

5183-1295: Was delivered to Nokia Mobile Phones Ltd, which launched the first SMR-FBAR-based GSM three-band mobile phone product in 2001. Infineon's FBAR (BAW) filter group was acquired by Avago Technologies Ltd 2008 which later became part of Broadcom as described before. After acquiring Panasonic's filtering business in 2016 Skyworks Solutions became one of the major players in BAW/FBAR devices additionally to Broadcom and Qorvo. Additionally after acquiring rest of RF360 Holdings in 2019 Qualcomm and Kyocera are offering thin film resonator based products like RFFE modules and separate filters. Still many companies like Akoustis Technologies, Inc. (founded in 2014), Saiwei Electronics, Texas Instruments (TI), several universities and research institutes are offering and studying to improve FBAR technology, its performance, manufacturing capacity, advancing design capabilities of FBARs and exploring new application areas jointly with system manufacturers and companies providing simulation tools ( Ansys , Comsol Multiphysics, and Resonant Inc. etc.). Companies in acoustics have also found thin film piezoelectric resonators for miniaturising speakers. Because thin film resonators can replace crystals in sensoring,

5256-403: Was evaporated on a resonant piece of bulk quartz crystal which served as a transducer providing a Q factor (quality factor) of 5000 at the resonance frequency (279 MHz). This was an enabler for tighter frequency control, for needs to use higher frequencies and utilising FBAR resonators. With the development of thin film technologies it was possible to keep the Q factor high enough, leave out

5329-435: Was one of the pioneering companies in the field of FBAR resonators and filters mostly for space and military applications. The first products were delivered to customers in 1997. TFR Technologies Inc. was in 2005 acquired by TriQuint Semiconductor Inc. In early 2015, RF Micro Devices (RFMD), Inc. and TriQuint Semiconductor, Inc. announced a merger to form Qorvo active providing FBAR-based products. HP Laboratories started

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