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Author

Masafumi Iwaki

Other affiliations: Taiyo Yuden
Bio: Masafumi Iwaki is an academic researcher from Fujitsu. The author has contributed to research in topics: Resonator & Duplexer. The author has an hindex of 18, co-authored 50 publications receiving 854 citations. Previous affiliations of Masafumi Iwaki include Taiyo Yuden.

Papers
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Patent
27 Apr 2007
Proceedings ArticleDOI
23 Aug 2004
TL;DR: In this article, the authors investigated the influence of electrode materials on the resonant characteristics of FBAR in FEM simulations and experiments and found the properties of ruthenium (Ru) to be suitable for use as electrode materials for AlN-based FBARs.
Abstract: We have developed a new electrode material, suitable for AlN-based FBARs. The necessary conditions for FBAR electrode materials are low density, low resistivity, and high acoustic impedance. We investigated the influence of electrode materials on the resonant characteristics of FBAR in FEM simulations and experiments. We found the properties of ruthenium (Ru) to be suitable for use as electrode materials for AlN-based FBARs. In addition, by smoothing the surface of the electrodes, full width at half-maximum (FWHM) of the X-ray rocking curves of the AlN films is found to be 2.9/spl deg/ on Ru electrodes. The resonant characteristics of FBAR using Ru electrodes were an unloaded resonant quality factor, Q/sub r/, of 3585 and an effective electromechanical coupling coefficient, k/sup 2/, of 6.6% at 5 GHz. Furthermore, we applied these resonators to ladder-type FBAR filters for 5 and 2 GHz. As a result, we achieved low-loss and high-Q FBAR filters with Ru electrodes.

70 citations

Patent
01 Nov 2012
TL;DR: In this article, a filter includes one or a plurality of parallel resonators coupled in parallel and one or plurality of a film bulk acoustic resonator coupled in series, the substrate having a substrate, a lower electrode, a piezoelectric membrane, and an upper electrode, where at least one of the lower electrode and the upper electrode has a thick membrane region having a thickness larger than that of a center portion of a resonance region at an edge of the resonance region.
Abstract: A filter includes one or a plurality of parallel resonators coupled in parallel and one or a plurality of a film bulk acoustic resonators coupled in series, the film bulk acoustic resonator having a substrate, a lower electrode, a piezoelectric membrane, and an upper electrode, wherein: at least one of the lower electrode and the upper electrode has a thick membrane region having a thickness larger than that of a center portion of a resonance region at an edge of the resonance region, the resonance region being a region where the lower electrode and the upper electrode face with each other through the piezoelectric membrane; and a width of the thick membrane region is smaller than a wavelength of an acoustic wave propagating in a direction crossing a thickness direction of the piezoelectric membrane.

59 citations

Patent
08 Aug 2006
TL;DR: In this paper, a duplexer includes an antenna terminal, a first filter connected to the antenna terminal and a second filter connected at the same time to the duplex terminal.
Abstract: A duplexer includes an antenna terminal, a first filter connected to the antenna terminal, and a second filter connected to the antenna terminal. At least one of the first filter and the second filter is a ladder type filter in which a parallel resonator and multiple series resonators are included, one or more first inductors are respectively connected in parallel with one or more series resonators out of the multiple series resonators, and one of the one or more first inductors is connected in parallel with one of the multiple series resonators that is arranged closest to the antenna terminal.

56 citations

Patent
04 Aug 2009
TL;DR: In this article, a piezoelectric thin-film resonator is defined as a resonator with a substrate, a lower electrode formed on the substrate and an upper electrode created by the lower electrode and the upper electrode opposing each other through the substrate to form an opposing region, the opposing region including a space at a boundary of the opposing regions.
Abstract: A piezoelectric thin film resonator includes a substrate, a lower electrode formed on the substrate, a piezoelectric film formed on the lower electrode, and an upper electrode formed on the piezoelectric film, the lower electrode and the upper electrode opposing each other through the piezoelectric film to form an opposing region, the opposing region including a space at a boundary of the opposing region. The space extends from an innerside to an outer side of the opposing region and is formed in or on the piezoelectric film.

46 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the authors review the current state of the art of MEMS devices and subsystems for lightwave communication applications, which can either be broadband (wavelength independent) or wavelength selective.
Abstract: The intensive investment in optical microelectromechanical systems (MEMS) in the last decade has led to many successful components that satisfy the requirements of lightwave communication networks. In this paper, we review the current state of the art of MEMS devices and subsystems for lightwave communication applications. Depending on the design, these components can either be broadband (wavelength independent) or wavelength selective. Broadband devices include optical switches, crossconnects, optical attenuators, and data modulators, while wavelength-selective components encompass wavelength add/drop multiplexers, wavelength-selective switches and crossconnects, spectral equalizers, dispersion compensators, spectrometers, and tunable lasers. Integration of MEMS and planar lightwave circuits, microresonators, and photonic crystals could lead to further reduction in size and cost

341 citations

Patent
24 May 2012
TL;DR: In this paper, a hemodialysis system consisting of a user interface model layer, a therapy layer, below the UIs, and a machine layer below the therapy layer is described.
Abstract: Dialysis systems comprising actuators that cooperate to perform dialysis functions and sensors that cooperate to monitor dialysis functions are disclosed. According to one aspect, such a hemodialysis system comprises a user interface model layer, a therapy layer, below the user interface model layer, and a machine layer below the therapy layer. The user interface model layer is configured to manage the state of a graphical user interface and receive inputs from a graphical user interface. The therapy layer is configured to run state machines that generate therapy commands based at least in part on the inputs from the graphical user interface. The machine layer is configured to provide commands for the actuators based on the therapy commands.

258 citations

Journal ArticleDOI
Clemens Ruppel1
TL;DR: This paper will try to focus on innovations leading to high volume applications of intermediate frequency (IF) and radio frequency (RF) acoustic filters, e.g., TV IF filters, IF filters for cellular phones, and SAW/BAW RF filters for the RF front-end of cellular phones.
Abstract: Today, acoustic filters are the filter technology to meet the requirements with respect to performance dictated by the cellular phone standards and their form factor. Around two billion cellular phones are sold every year, and smart phones are of a very high percentage of approximately two-thirds. Smart phones require a very high number of filter functions ranging from the low double-digit range up to almost triple digit numbers in the near future. In the frequency range up to 1 GHz, surface acoustic wave (SAW) filters are almost exclusively employed, while in the higher frequency range, bulk acoustic wave (BAW) and SAW filters are competing for their shares. Prerequisites for the success of acoustic filters were the availability of high-quality substrates, advanced and highly reproducible fabrication technologies, optimum filter techniques, precise simulation software, and advanced design tools that allow the fast and efficient design according to customer specifications. This paper will try to focus on innovations leading to high volume applications of intermediate frequency (IF) and radio frequency (RF) acoustic filters, e.g., TV IF filters, IF filters for cellular phones, and SAW/BAW RF filters for the RF front-end of cellular phones.

210 citations

Journal ArticleDOI
TL;DR: In this article, a film bulk acoustic resonator (FBAR) mass sensor is described, which is built on a micromachined silicon-nitride diaphragm with a piezoelectric thin film and Al electrodes.
Abstract: This paper describes a highly sensitive, film bulk acoustic resonator (FBAR) mass sensor (built on a micromachined silicon-nitride diaphragm with a piezoelectric thin film and Al electrodes) that can operate in vapor and liquid. The sensitivity of the device to mass change on its surface has been investigated by having various thicknesses of silicon-nitride support layer and also of Al layer. The sensor is measured to have a mass sensitivity of 726 cm/sup 2//g, which is about 50 times that of a typical quartz crystal microbalance (QCM). In vapor, the sensor (operating at around 1 GHz and having a relatively high quality (Q) factor of 200-300) shows a minimum detectable frequency shift of about 400 Hz, which corresponds to a mass change of 10/sup -9/ g/cm/sup 2/ on the sensor surface, comparable with that detectable by a QCM. In liquid, though the Q usually drops more than an order of magnitude, we obtain a Q of 40 at 2 GHz by using a second harmonic resonance of the resonator. And with the Q, a minimum 5 ppm resonant frequency shift can be detected, which corresponds to 10/sup -8/ g/cm/sup 2/ change on the sensor surface.

191 citations

Patent
31 May 2006
TL;DR: In this article, the film bulk acoustic resonators (FBARs) stacked with stacked FBARs including at least two curved edges are disclosed. But the authors did not specify the number of curved edges.
Abstract: Film bulk acoustic resonators (FBARs) stacked FBARs (SBARS) including at least two curved edges are disclosed.

164 citations