Showing papers on "Q factor published in 2001"

Thin film bulk wave acoustic resonators (FBAR) for wireless applications

Abstract: For some time, FBAR technology has lagged behind ceramic technology and surface acoustic wave resonator (SAW) technology for commercial applications. There were several technologies that had to be developed before FBAR technology became viable for rf filters. First, a process is needed that can make the resonators manufacturable, robust and repeatable. Second, maximizing the coupling coefficient, k/sub t//sup 2/ and the Q of the resonator (k/sub t//sup 2/ Q product) is necessary. Another technology needed is a method to eliminate ripple (or "suck out") associated with lateral mode excitation. Lastly, a method is needed for maintaining a uniform thickness (for frequency control and a means to target frequency to within +-0.03%). If one overcomes these sets of hurdles, the rewards are high. The Quality factor, Q, inherent in these structures is impressive (over 2500) and the intrinsic k/sub t//sup 2/ has been inferred to be close to the theoretical maximum of 6.5%. The k/sub t//sup 2/ Q product (Figure of Merit for FBAR filters) have been as high as 100 for our devices. These two properties can be combined in a filter to achieve low pass band insertion loss and extremely sharp skirts. One intrinsic advantage of FBAR over SAW technology is the ability to handle input power in excess of 4 Watts. Resistance to Electrical Static Discharge (ESD) is another desirable property of FBAR devices. Finally, FBAR technology is intrinsically a "low temperature" process technology-compatible with semiconductor technology. This implies future integration of FBARs with semiconductor circuits.

Loss mechanisms in piezoelectrics: how to measure different losses separately

Abstract: Losses in piezoelectrics are considered in general to have three different mechanisms: dielectric, mechanical, and piezoelectric losses. This paper deals with the phenomenology of losses first, then how to measure these losses separately in experiments. We found that heat generation at off-resonance is caused mainly by dielectric loss tan /spl delta/' (i.e., P-E hysteresis loss), not by mechanical loss, and that a significant decrease in mechanical Q/sub m/ with an increase of vibration level was observed in resonant piezoelectric ceramic devices, which is due to an increase in the extensive dielectric loss, not in the extensive mechanical loss. We propose the usage of the antiresonance mode rather than the conventional resonance mode, particularly for high power applications because the mechanical quality factor Q/sub B/ at an antiresonance frequency is larger than Q/sub A/ at a resonance frequency.

High-Q LTCC-based passive library for wireless system-on-package (SOP) module development

Abstract: In this paper, we present the development and full characterization and modeling of a multilayer ceramic-based system-on-package component library. Compact high-Q three-dimensional inductor and capacitor topologies have been chosen and incorporated. A measured inductor Q factor as high as 100 and self-resonant frequency as high as 8 GHz have been demonstrated. The new vertically interdigitated capacitor topology occupies nearly an order of magnitude less of real estate while demonstrating comparable performance to the conventional topology. The low-temperature co-fired ceramic (LTCC) library has been incorporated into a 1.9-GHz CMOS power-amplifier design exhibiting a measured 17-dB gain, 26-dBm output power, and 48% power added efficiency. This power-amplifier module with fully integrated LTCC passives demonstrates a superior performance to those with full and partial on-chip passive integration.

Uniplanar one-dimensional photonic-bandgap structures and resonators

Abstract: This paper presents uniplanar one-dimensional (1-D) periodical structures, so-called photonic-bandgap (PBG) structures, and defect high-Q resonators for coplanar waveguide, coplanar strip line, and slot line. Proposed uniplanar PBG structures consist of 1-D periodically etched slots along a transmission line or alternating characteristic impedance series with wide band-stop filter characteristics. A stop bandwidth obtained is 2.8 GHz with a stopband rejection of 36.5 dB. This PBG performance can be easily improved if the number of cells or the filling factor is modified in a parametric analysis. Using uniplanar 1-D PBG structures, we demonstrate new high-Q defect resonators with full-wave simulation and measured results. These structures based on defect cavity or Fabry-Perot resonators consist of a center resonant line with two sides of PBG reflectors. They achieve a loaded Q of 247.3 and unloaded Q of 299.1. The proposed circuits should have many applications in monolithic and hybrid microwave integrated circuits.

Microtorus: a high-finesse microcavity with whispering-gallery modes

Abstract: We demonstrate a 165-mu;m oblate spheroidal microcavity with a free spectral range of 383.7 GHz (3.06 nm), a resonance bandwidth of 23 MHz (quality factor Q approximately 10(7)) at 1550 nm, and finesse F>/=10(4) . The highly oblate spheroidal dielectric microcavity combines a very high Q factor, typical of microspheres, with a vastly reduced number of excited whispering-gallery modes (by 2 orders of magnitude). The very large free spectral range in this novel microcavity-a few hundred gigahertz instead of a few gigahertz as in typical microspheres-is desirable for applications in spectral analysis, narrow-linewidth optical and rf oscillators, and cavity QED.

Synthesis of a parallel-coupled ring-resonator filter

Abstract: An effective and exact synthesis technique for the design of parallel-coupled ring-resonator filters with a maximally flat stop-band characteristic of any order is presented. Simple closed-form formulas determine the Q factor of each resonator and the coupling coefficients. The performances of these filters are discussed for their applications as interleavers and channel-dropping filters in wavelength-division multiplexing systems.

Compact damping models for laterally moving microstructures with gas-rarefaction effects

Abstract: Compact models for the viscous damping coefficient in narrow air gaps between laterally moving structures are reported. In the first part of the paper, a simple frequency-independent first-order slip-flow approximation for the damping coefficient is derived and compared with a more accurate expression obtained from the linearized Boltzmann equation. The simple approximation is slightly modified and fitted to match the accurate model. The resulting simple approximation has a maximum relative error of less than /spl plusmn/6% at arbitrary Knudsen numbers in viscous, transitional and free molecular regions. In the second part of the paper, dynamic models for the damping force are derived, considering again gas rarefaction, by applying various boundary conditions. The damping admittance of the first-order slip-flow model is implemented also as an electrical equivalent admittance, constructed of RC sections, to allow both frequency and time domain simulations with a circuit simulator. The dependence of the damping admittance on pressure and gap displacement is demonstrated with model simulations. The accuracy and validity range of the model are verified with comparative numerical simulations of the Navier-Stokes equation. Finally, the damping coefficient in a lateral resonator is calculated using the compact model and compared with measured data with good agreement.

Electromechanical model of a resonating nano-cantilever-based sensor for high-resolution and high-sensitivity mass detection

Abstract: A simple linear electromechanical model for an electrostatically driven resonating cantilever is derived. The model has been developed in order to determine dynamic quantities such as the capacitive current flowing through the cantilever-driver system at the resonance frequency, and it allows us to calculate static magnitudes such as position and voltage of collapse or the voltage versus deflection characteristic. The model is used to demonstrate the theoretical sensitivity on the attogram scale of a mass sensor based on a nanometre-scale cantilever, and to analyse the effect of an extra feedback loop in the control circuit to increase the Q factor.

Sandwich-type ferromagnetic RF integrated inductor

Abstract: The first demonstration of a sandwich-type ferromagnetic RF integrated spiral inductor for the 2-GHz range is reported. Two ferromagnetic CoNbZr films were set to sandwich the spiral in order to enhance the amount of magnetic flux linkage across the coil current. The stresses given from the insulator to the ferromagnetic film were studied. The inductance L of 7.9 nH and the qualify factor Q of 12.7 were obtained for a 200 /spl mu/m/spl times/400 /spl mu/m size four-turn rectangular spiral at f=2 GHz. The inductance was better than that of an air core of the same coil size by 19%, and the Q was better by 23%. Comparison with the on-top magnetic film type was also discussed.

Optically pumped parametric amplification for micromechanical oscillators

Abstract: Micromechanical oscillators in the rf range were fabricated in the form of silicon discs supported by a SiO2 pillar at the disk center. A low-power laser beam, (Plaser∼100 μW), focused at the periphery of the disk, causes a significant change of the effective spring constant producing a frequency shift, Δf(Δf/f∼10−4). The high quality factor, Q, of the disk oscillator (Q∼104) allows us to realize parametric amplification of the disk’s vibrations through a double frequency modulation of the laser power. An amplitude gain of up to 30 was demonstrated, with further increase limited by nonlinear behavior and self-generation. Phase dependence, inherent in degenerate parametric amplification, was also observed. Using this technique, the sensitivity of detection of a small force is greatly enhanced.

Self-assembling MEMS variable and fixed RF inductors

Abstract: Inductors play a key role in wireless front-end circuitry, yet are not generally well suited for conventional RF integrated-circuit (RFIC) fabrication processes. We have developed inductors that can be fabricated on a conventional RFIC silicon substrate, which use warping members to assemble themselves away from the substrate to improve quality factor (Q) and self-resonance frequency (SRF), and to provide a degree of variation in inductance value. These self-assembling variable inductors are realized through foundry provided microelectromechanical systems (MEMS) processing and have demonstrated temperature stable Q values greater than 13, SRF values well above 15 GHz, and inductance variations greater than 18%. Simulations suggest the potential for Q values above 20 and inductance variations greater than 30%, with optimized processing.

Resonance frequency and Q factor mapping by ultrasonic atomic force microscopy

Abstract: We developed an improved ultrasonic atomic force microscopy (UAFM) for mapping resonance frequency and Q factor of a cantilever where the tip is in linear contact with the sample. Since the vibration amplitude at resonance is linearly proportional to the Q factor, the resonance frequency and Q factor are measured in the resonance tracking mode by scanning the sample in the constant force mode. This method enables much faster mapping of the resonance frequency and Q factor than the previous one using a network analyzer. In this letter, we describe the principle and instrumentation of the UAFM and show images of carbon-fiber-reinforced plastic composites.

High-performance inductors

Abstract: In this paper, we describe the design, test data, and analysis of several circular spiral inductors fabricated on GaAs substrates using the multifunction self-aligned gate multilayer process. Various factors such as high inductance, high-quality and, high current handling capacity, and compactness are studied. Several configurations for inductors were investigated to optimize the inductor geometry such as the linewidth, spacing between the turns, conductor thickness, and inner diameter. It includes measured effects of various parameters on inductor performance, such as linewidth, spacing, inner diameter, metal thickness, underlying dielectric, and dielectric thickness. It is shown experimentally that the Q factor of spiral inductors can be enhanced by using 9-/spl mu/m-thick metallization and placing inductors on a 10-/spl mu/m-thick polyimide layer, which is placed on top of the GaAs substrate. Using this technique, we have observed up to 93% improvement in the Q factor of circular spiral inductors, as compared to standard spiral inductors fabricated on GaAs substrates. Inductors having thick metallization can also handle dc currents as large as 0.6 A.

High Q inductor add-on module in thick Cu/SiLK/sup TM/ single damascene

Abstract: Thick Cu single damascene inductors with very high Q factors are integrated on top of a standard aluminum 3LM BEOL process. Obtained Q factors are more than four times higher than Q factors of the inductors of the same geometry processed in the Al 3LM BEOL. For an inductor of 2.8 nH inductance, a Q peak of 24 at 2 GHz was reached by using 4 /spl mu/m thick Cu on a 2 /spl mu/m IMD oxide layer.

HIRF penetration through apertures: FDTD versus measurements

Abstract: The penetration of high-intensity radiated fields (HIRF) into conducting enclosures via apertures is an EMI issue that is relevant to all aviation. The stories are numerous, of disrupted communications, disabled navigation equipment, etc., due to the effects of EM sources external to the aircraft. Here, the FDTD method is used to predict the shielding effectiveness of conducting enclosures with apertures, and the numerical results are compared with measurements. Several issues related to the FDTD analysis of highly resonant and high-quality factor (high-Q) structures, such as windowing and acceleration techniques, are examined and discussed.

Micromachined RF MEMS tunable capacitors using piezoelectric actuators

Abstract: In this paper, RF MEMS tunable capacitors with low operation voltage, high linearity, high quality factor, and large tuning ratio have been fabricated by utilizing micromachined piezoelectric actuators. The fabricated tunable capacitor has a C/sub max//C/sub min/ ratio of 3.1 to 1 at bias voltages of 6 V and a quality factor of 210 at 1 GHz.

Accurate modeling of high-Q spiral inductors in thin-film multilayer technology for wireless telecommunication applications

Abstract: In the current trend toward portable applications, high-Q integrated inductors are gaining a lot of importance. Using thin-film multilayer or multichip-module-deposition technology, high-Q circular inductors for RF and microwave applications may be integrated efficiently. Their quality factors may go up to over 100. In this paper, an accurate analytical model for such multiturn circular spiral inductors embedded in a thin-film multilayer topology is presented. Starting from the geometrical parameters, the model provides an accurate prediction of the inductance value, Q factor and frequency behavior of the inductor. This allows a "first-time-right?" realization of the integrated component and provides opportunities for fast optimization of the inductors. Finally, the presented high-Q inductors have been used in various integrated RF and microwave subsystems for wireless applications, of which a number are discussed at the end of this paper.

Piezoelectric materials for BAW resonators and filters

Abstract: Thin film bulk acoustic wave (BAW) resonators and filters are appropriate for mobile communication systems operating at high frequencies between 0.5 and 10 GHz. c-axis orientated AlN films are used for medium bandwidth applications. Electromechanical coupling factors k/sub t/ of 0.25/spl plusmn/0.03, which are close to the bulk data, have been found in AlN thin films using optimum sputter conditions. The correlation between k/sub t/ and AlN film orientation is discussed. Resonator Q values of approx. 450 are reported at 2.6 GHz and a Q of 250 was realized at 9.2 GHz. A physical model is shown to accurately predict the frequency responses of BAW resonators and band-pass filters. For wide bandwidth applications PbZr/sub x/Ti/sub 1-x/O/sub 3/ (PZT) films are investigated. They exhibit large coupling coefficients.

High-power resonant measurements of piezoelectric materials: Importance of elastic nonlinearities

Abstract: A resonance method for measuring the complex elastic and electromechanical properties of piezoelectric materials under high-power operational conditions has been developed. In this method, rectangular specimens are piezoelectrically driven into mechanical resonance. The displacement of the transverse resonance mode is measured as a function of frequency (f ) using an optical vibrometer method in conjunction with a frequency response analyzer. Due to the wide amplitude sensitivity range of the detection system, asymmetries in nonlinear resonance curves with mechanical damping can be accurately measured. The method has been applied to the study of Pb(Zr1−xTix)O3. Under resonant high-power drive, it has been found that electromechanical nonlinearities are due to elastic ones, as the elastic and electromechanical properties were both found to scale with the square of the strain amplitude. The temperature (T) and ac electric field (Eac) dependence of the mechanical quality factor Qm were also determined. Iso-Q...

Dielectric resonators raise your high-Q

Abstract: High-quality resonating elements are the key to the function of most microwave circuits and systems. They are fundamental to the operation of filters and oscillators, and the performance of these circuits is primarily limited by the resonator quality factor. At microwave frequencies, the quality factor (Q) of metal transmission line resonant circuits is proportional to volume. As a result, waveguide structures are often employed to increase Q at the expense of size, weight, and cost. Dielectric resonators overcome these limitations due to the fact that their losses are dominated by dielectric loss (loss tangent), and only in small part to metallic losses (housing). Dielectric losses are improving constantly, whereas metal losses, with the exception of superconductors, have remained substantially the same. These resonators can be made to perform the same functions as waveguide filters, but are, in contrast, very small, stable and lightweight. The popularization of low-loss dielectric resonators roughly coincides with the miniaturization of many of the other associated elements of most microwave circuits. When taken together, these technologies permit the realization of small, reliable, lightweight and stable microwave systems.

Frequency-tunable microwave dielectric resonator

Abstract: A new type of tunable composite dielectric resonator (DR) has been designed, In the structure of this DR, a controllable insert was used to change the resonance frequency (f/sub 0/) in a wide spectral range, while preserving a high quality factor. The simplest of proposed resonance systems for obtaining f/sub 0/ control is a microwave DR crossed by an air slot, which is controlled by fast piezoelectric actuator. Analytical and experimental techniques were employed for optimization of the composite DR structure. It has been observed that this device can create a change up to 20%-25% in its resonance frequency.

Low-phase-noise LC quadrature VCO using coupled tank resonators in a ring structure

Abstract: The concept of coupled resonators is employed in a ring VCO structure to reduce the phase noise. This architecture allows the design of low-phase-noise voltage controlled oscillators (VCOs) using integrated low-Q inductors. Quadrature differential outputs are also realized in this design. Two monolithic LC tanks are coupled together to implement a transimpedance resonator with an effective Q close to twice that of a single tank. In addition, the coupled tank's transimpedance resonator provides 90/spl deg/ phase shift. Four such stages are cascaded in a ring structure to provide I-Q differential outputs, and to further reduce the phase noise. A prototype of the VCO is built in a 0.35-/spl mu/m CMOS technology. The measured phase noise is -122 dBc/Hz at 600-kHz offset from 1.93 GHz. The VCO draws 9.2 mA from a 3-V supply, and occupies a chip area of 1.1/spl times/1.1 mm/sup 2/.

A high-Q reconfigurable planar EBG cavity resonator

Abstract: A reconfigurable planar electromagnetic bandgap (EBG) cavity resonator has been designed, fabricated, and tested. The resonator, based on a microstrip-coupled cavity constructed with periodic metallic post side walls, resonates at 10.60 GHz or 8.63 GHz, depending on the state of two rows of switchable post elements. Fabricated on 0.031 inch 5880 Duroid, the resonator exhibits Qs of 348 and 274 for the 10.60 GHz and 8.63 GHz resonances, respectively. In addition to the reasonably high Qs achievable with this design, the circuit utilizes standard printed circuit board (PCB) fabrication techniques and is 100% compatible with commercial PCB processes, enabling low-cost mass production.

Direct measurement of the quality factor in a two-dimensional photonic-crystal microcavity.

Abstract: A new microcavity design is proposed and structures are realized with a two-dimensional photonic-crystal slab. The cavity consists of seven defect holes that encompass a hexagon and is designed to reduce vertical light leakage. From a direct transmission measurement, a Q value of 816+/-30 is achieved at lambda =1.55 mum . This high- Q cavity will permit the realistic realization of spontaneous-emission modification and on-off optical switches.

Analysis and numerical simulation of eigenmode characteristics for semiconductor lasers with an equilateral triangle micro-resonator

Abstract: The eigenmodes confined in the equilateral triangle resonator (ETR) are analyzed by deriving the eigenvalues and the mode field distributions and by the finite difference time domain (FDTD) technique. The analytical results show that the one-period-length for the mode light rays inside the ETR is the perimeter of the ETR, and the number of transverse modes is limited by the condition of total internal reflection. In addition, the sum of the longitudinal mode index and the transverse mode index should be an even number, which limits the number of confined modes again. Based on the FDTD technique and the Pade approximation, we calculate the mode resonant frequencies and the quality factors from the local maximum and the width of the spectral distribution of the intensity. The numerical results of mode frequencies agree very well with the analytical results, and the quality factor of the fundamental mode is usually higher than that of the higher order transverse modes. The results show that the ETR is suitable to realize single-mode operation as semiconductor microcavity lasers.

Investigating surface stress: Surface loss in ultrathin single-crystal silicon cantilevers

Abstract: We investigated the effect of surface treatment in an ultrahigh-vacuum chamber on the Q factor of ultrathin single-crystal silicon cantilevers with different thicknesses (60, 170, and 500 nm) and different surface orientations. When the length is L>30 μm, the Q factor is proportional to the thickness and surface loss dominates, whereas when L<30 μm, support loss surpasses the surface loss. Heating can remove the SiO2 layer and absorbates and results in an increase of the Q factor. Hydrogen termination leads to a larger relative increase of the Q factor in thinner structures than in thicker ones. Heating and H exposure improve the Q values of Si(100)-oriented cantilevers more than Si(110)-oriented ones, and they result in the opposing resonance frequency response for these two surfaces.

High Q factor MEMS resonators

Abstract: Microelectromechanical resonators (102) that can be fabricated on a semiconductor die by processes normally used in fabricating microelectronics (e.g., CMOS) circuits are provided. The resonators comprises at least two vibratable members (112, 114) that are closely spaced relative to a wavelength associated with their vibrating frequency, and driven to vibrate one-half a vibration period out of phase with each other, i.e. to mirror each others motion. Driving the vibratable members as stated leads to destructive interference effects that suppress leakage of acoustic energy from the vibratable members into the die, and improve the Q-factor of the resonator. Vibratable members in the form of vibratable plates that are formed by deep anisotropic etching one or more trenches (110, 112, 114) in the die are disclosed. Embodiments in which two sets of vibratable plates are spaced by 1 the aforementioned wavelength to further suppress acoustic energy leakage, and improve the Q-factor of the resonator are disclosed.

Accuracy issues in surface resistance measurements of high temperature superconductors using dielectric resonators (corrected)

Abstract: Reproducible and accurate measurements of the surface resistance of high temperature superconductors are essential for the development and commercialization of the next generation of high performance cryoelectronic systems. Dielectric resonators are the best, most accurate technique for this measurement and have been suggested for the international standard technique. This paper discusses trade-offs amongst the various types of dielectric resonators including choices of the dielectric rod, the metallic enclosure, the electrical measurements of Q-factor, resonant frequency and coupling coefficients, and other issues to ensure reproducible and accurate measurements.

Simplified method for measurements and calculations of coupling coefficients and Q/sub 0/ factor of high-temperature superconducting dielectric resonators

Abstract: To accurately determine the surface resistance of high-temperature superconducting films, multifrequency measurements of S/sub 21/, S/sub 11/, and S/sub 22/ and sophisticated data processing are required. As a result, surface resistance measurements and calculations for varying temperatures are very time consuming. In this paper, we introduce a simplified method for calculations of the unloaded Q (Q/sub 0/) factor, which require measurements of S/sub 11/ and S/sub 22/ at the lowest temperature only. For all other temperatures, only S/sub 21/ measurements are needed. The method has been shown to give sufficiently accurate Q/sub 0/ values and, hence, the surface resistance of superconducting samples, as compared to results obtained from S/sub 21/, S/sub 11/, and S/sub 22/ measurements using the transmission-mode Q factor technique. The presented method has been tested under different coupling coefficients and frequencies.

MEMS high Q microwave inductors using solder surface tension self-assembly

Abstract: We present microwave inductors of 1.5 to 2.5 nH fabricated out-of-plane by a self-assembly process. The consequent de-coupling from the substrate allows improved Q (from 4 to 20) and frequency of maximum Q (from 0.5 GHz to 3 GHz) on low resistivity silicon substrates.