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Aluminum nitride (AlN) Lamb wave resonators (LWRs) utilizing the lowest symmetric (S0) mode have attracted much interests since they have high frequencies, low motional impedances, and capability of multiple frequencies on a single chip. However, the transverse spurious modes are often strong in AlN LWR, and largely degrade the performance in application, so suppression the transverse mode is highly...
The constantly rising demand for higher data rates is addressed by advanced communication standards like carrier aggregation (CA) in combination with LTE. The increased complexity of the RF frontend has put tremendous pressure on improving linear performance of BAW filters over the last years. On top of that a large number of intermodulation (IMD) specification have been added to safeguard all CA...
AlN MEMS CMRs offer high Q and kt2, and a center frequency (f0) that can be primarily set by lithography. They also have direct 50 Ω matching capability. These properties make AlN CMRs an ideal candidate to synthesize multi-frequency bandpass filters on a single chip with low insertion loss (IL). However, their practical implementation is hindered by fabrication induced variations. To address this...
I.H.P. SAW (Incredible High-Performance SAW) has a novel multi-layered structure to confine SAW energy in substrate surface area, and it shows extremely high quality (Q) factor, low temperature coefficient of frequency (TCF) and improved electromechanical coupling coefficient (K2). This paper introduces its mechanism of the high acoustic Q factor, both theoretically and experimentally, and its applications...
Transmit filters comprising piezoelectric resonators are fabricated in a Thin Film Bulk Acoustic Resonator (FBAR) technology. A filter's 2nd harmonic emissions (H2), generated by the resonators in the filter's output stage must be sufficiently small to prevent the filter from desensitizing a nearby receiver. Anti-parallel and anti-series connected resonator configurations, in which the H2 emissions...
Spurious modes (SMs) result in in-band ripples and degrade the out-of-band rejection of filters, thus impeding the synthesis of high performance filters with MEMS resonators. Therefore, the ability to predict the presence of SMs in specific resonator geometries is highly desired and different techniques have been explored such as: 1-D/2-D analytic models, and 2-D/3-D finite element methods (FEM)....
Mobile filters are required to process increasing RF power levels, driven by the need for higher data-rates and improved cell-edge coverage. This results in more demanding filter specifications for loss, rejection, isolation, linearity and reliability, while, at the same time, handset OEMs require smaller filter footprints.
Factors limiting the isolation of conventional miniaturized filters and duplexers have been considered in the literature. They can be classified into two types of signal leakage: one occurs via the main signal path due to the finite impedance of the RX filter in the TX band in a duplexer; the second one is due to electromagnetic feedthrough (EMF), electromagnetic couplings or imperfect grounding....
The frequency switchable filters are suitable for selecting the vacant frequency bands. Usual polarity unidirectional single-layered resonators excite 1st mode whereas polarity inverted two-layered resonators excite 2nd mode. We previous reported the frequency switchable two-layered PZT/PbTiO3 epitaxial film resonators[1]. However, PbTiO3 films grown on PZT/PbTiO3 films are difficult to obtain since...
High frequency bands such as LTE band 42 and band 43 require resonators and filters that can operate at frequencies higher than 3 GHz. However, existing lithium niobate fundamental symmetric (S0) lamb mode resonators and surface acoustic wave (SAW) resonators have operating frequency limitations (<2 GHz) due to their low phase velocities. High frequency AlN film bulk acoustic resonators (FBARs)...
Power dividers/combiners are used as fundamental unit for power combining/splitting in different RF/Microwave circuits such as power amplifier modules, antenna array feeds or mixers. Most common types are based on quarter wave transmission line and their miniaturization is challenging especially in frequency less than GHz range where they exhibit very large physical size that make their use impractical...
Linearity of RF filters is in the focus of system-architects as carrier aggregation (CA) schemes in down- and uplink emerge as a requirement. The nonlinear electro-thermal-acoustic constitutive equations of the piezoelectricity and the number of different materials involved in the manufacturing of BAW resonators make it difficult to discern between different sources of nonlinearity. It is hard to...
Usually, the design of acoustic wave devices is mainly entrusted to optimization techniques due to the stringent constraints imposed by the technological feasibility of acoustic resonators and the challenging electrical specifications. A stringent transmission response and very restrictive technological factors make the designing a complex and challenging task. The objective of this work is to describe...
Mark Twain said “There is no such thing as a new idea. It is impossible. We simply take a lot of old ideas and put them into a sort of mental kaleidoscope. We give them a turn and they make new and curious combinations. We keep on turning and making new combinations indefinitely; but they are the same old pieces of colored glass that have been in use through all the ages.” This sentiment rings true...
Recent trends in RF filter design has brought the necessity to design SAW resonators with boosted performance. Most importantly, improvements in both the resonators' quality factors (Q) and temperature coefficient of frequency (TCF) are needed. TC-SAW concept employing 128 Y-cut LiNbO3 has attracted considerable practical interest in this view. Some excellent works from Qorvo have demonstrated the...
Linearity requirements in BAW modules intensified drastically over the past years. While an optimized filter and module design can improve the overall floor of the non-linear response efficiently, often unavoidable effects of parasitics in a BAW chip require more advanced techniques to meet the part's specification requirements. In this article, we present a novel approach to further linearize the...
Film bulk acoustic wave resonator (FBAR) filters are promising for the mobile communication devices. Frequency switchable filters are suitable for selecting the vacant frequency bands. Usual polarity unidirectional single layer resonator excites fundamental mode whereas polarity inverted double layer resonator excites second mode. In this study, we considered that polarity inverted structure is easily...
We demonstrated the statistical element selection (SES) technique with an array of 1.15 GHz AlN MEMS subfilters fabricated in an 8” Si fabrication facility by A∗STAR, Institute of Microelectronics (IME), Singapore. The chip integration is achieved through a split-fab process where the hermetically thin-film-encapsulated (TFE) MEMS resonators are solder-bump bonded to a CMOS chip fabricated in a Samsung...
A compact filtering power divider/combiner using surface acoustic wave (SAW) technology for low frequency applications is presented. The proposed power divider/combiner is based on parallel connected SAW coupled resonator filters providing a dual functional capability as well as a higher level of miniaturization. The designed structure is a 3 way power divider/combiner that exhibits a passband-filtering...
Recent trends in cellular handsets demand SAW resonators with increased performance. Most importantly, improvements in both the resonators' quality factor (Q) and temperature coefficient of frequency (TCF) are needed. The TC-SAW concept employing buried Cu electrodes in SiO2/128°Y-LiNbO3 has attracted considerable practical interest in this view, with the requirement that the spurious transverse modes...
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