9,784 research outputs found

    Design of a New Step-like Frame FBAR for Suppression of Spurious Resonances

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    Film bulk acoustic wave resonators (FBARs) are of great interest for wireless applications due to its inherent advantages at microwave frequencies. However, the presence of spurious modes near the main resonance degrades the performance of resonators and requires development of new methods to suppress such unwanted modes. Different techniques are used to suppress these spurious modes. In this paper, we present design of a new step-like frame structure film bulk acoustic wave resonator operating near 1.5 GHz. The simulated results are compared with simple frame-like structure. The spurious resonances are eliminated effectively and smooth pass band is obtained with effective coupling coefficient of 5.68% and quality factor of 1800. The equivalent electrical mBVD model of the FBAR based on impedance response is also presented. These highly smooth phase response and passband skirt steepness resonators are most demanding for the design of low cost, small size and high performance filters, duplexers and oscillators for wireless systems

    A polarization insensitive ultrathin compact triple band metamaterial absorber

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    In this paper, design, characterization and measurements of an ultrathin compact polarization insensitive triple band metamaterial absorber for wide incident angle have been presented. The unit cell design consists of a Jerusalem cross shaped resonator inside a square loop resonator. The proposed absorber exhibits triple band absorption at 4.4, 6.48 and 15.44 GHz with 96.6% and 97.64% and 85.81% absorptivity, respectively, for wide incident angles of electromagnetic wave. The absorption frequencies can be effectively adjusted for C, X and Ku frequency bands by optimizing the dimensions of the absorber design. The proposed absorber is ultrathin (0.014 λ0) in thickness and compact (0.12 λ0) in size at the lowest frequency of absorption. The proposed absorber exhibits TE and TM polarization stability and provides high absorption up to the incident angle of 60°. A prototype of the proposed absorber structure has been fabricated and experimentally tested for normal and oblique incidences for TE and TM polarization. The measured responses have been observed in agreement with the simulated ones

    Possible ~ 1 hour quasi-periodic oscillation in narrow-line Seyfert 1 galaxy MCG--06--30--15

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    We found a possible ~ 1 hour quasi-periodic oscillation (QPO) in a ~ 55 ks X-ray observation of the narrow-line Seyfert 1 galaxy MCG--06--30--15 made with the XMM-Newton EPIC/pn detector in the energy range 0.3 -- 10 keV. We identify a total modulation of ~ 16% in the light curve and find a \simeq 3670~s quasi-period using Lomb-Scargle periodogram (LSP) and weighted wavelet Z-transform (WWZ) techniques. Our analyses of eight light curves of MCG--06--30--15, indicated the possible presence of an oscillation during one of them. The LSP indicates a statistically significant (\simeq 3σ\sigma) QPO detection. A WWZ analysis shows that the signal at this possible roughly 3670s period is present, and rather persistent, throughout the observation; however, a signal around 8735s is more persistent. We briefly discuss models that can produce X-ray QPOs with such periods in narrow line Seyfert 1 galaxies, as both other claimed QPO detections in this class of AGN had very similar periods.Comment: 5 pages, 4 figures, Published in A&A Letter

    Non-Fermi-liquid behavior at anti-ferromagnetic quantum critical point in heavy fermion system Ce(Cu1x_{1-x}Cox_x)2_2Ge2_2

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    Polycrystalline samples of Ce(Cu1x_{1-x}Cox_x)2_2Ge2_2 were investigated by means of electrical resistivity ρ\rho(TT), magnetic susceptibility χ\chi(TT), specific heat CCp_p(TT) and thermo electric power SS(TT) measurements. The long-range antiferromagnetic (AFM) order, which set in at TTN_N = 4.1 K in CeCu2_2Ge2_2, is suppressed by non-iso-electronic cobalt (Co) doping at a critical value of the concentration xxc_c = 0.6, accompanied by non-Fermi liquid (NFL) behavior inferred from the power law dependence of heat capacity and susceptibility i.e. CC(TT)/TT and χ\chi(TT) \propto TT1+λ^{-1+\lambda} down to 0.4 K, along with a clear deviation from TT2^2 behavior of the electrical resistivity. However, we have not seen any superconducting phase in the quantum critical regime down to 0.4 K.Comment: 8 pages, 11 figure

    Dynamic nuclear polarisation in biased quantum wires with spin-orbit interaction

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    We propose a new method for dynamic nuclear polarisation in a quasi one-dimensional quantum wire utilising the spin-orbit interaction, the hyperfine interaction, and a finite source-drain potential difference. In contrast with current methods, our scheme does not rely on external magnetic or optical sources which makes independent control of closely placed devices much more feasible. Using this method, a significant polarisation of a few per cent is possible in currently available InAs wires which may be detected by conductance measurements. This may prove useful for nuclear-magnetic-resonance studies in nanoscale systems as well as in spin-based devices where external magnetic and optical sources will not be suitable.Comment: 6 pages, published versio
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