5 Watt GaN HEMT Power Amplifier for LTE

This work presents the design and implementation of a stand-alone linear power amplifier at 2.4 GHz with high output power. A GaN HEMT transistor is selected for the design and implementation of the power amplifier. The device exhibits a gain of 11.7 dB and a drain efficiency of 39% for an output power of 36.7 dBm at 2.4 GHz for an input power of 25dBm. The carrier to intermodulation ratio is better than 25 dB for a two tone input signal of 25 dBm of total power and a spacing of 5 MHz. The fabricated device is also tested with LTE input signals of different bandwidths (5MHz to 20MHz)

Impurities and electronic localization in graphene bilayers

We analyze the electronic properties of bilayer graphene with Bernal stacking and a low concentration of adatoms. Assuming that the host bilayer lies on top of a substrate, we consider the case where impurities are adsorbed only on the upper layer. We describe non-magnetic impurities as a single orbital hybridized with carbon's pz states. The effect of impurity doping on the local density of states with and without a gated electric field perpendicular to the layers is analyzed. We look for Anderson localization in the different regimes and estimate the localization length. In the biased system, the field induced gap is partially filled by strongly localized impurity states. Interestingly, the structure, distribution and localization length of these states depend on the field polarization.Comment: 7 pages, 6 figure

Crítica de traduccions

Paul FRIEDLÄNDER, Platón : verdad del ser y realidad de la vida

Filtenna Integration Achieving Ideal Chebyshev Return Losses

This paper demonstrates that it is possible to find an ideal filter response (Chebyshew, Butterworth,..) considering the antenna as the last resonator of a filter under certain circumstances related with the antenna performance and the bandwidth of the filtenna device. If these circumstances are not accomplished, we can achieve excellent performance as well, by means of an iterative process the goal of which is defined by either a filter mask or a classical filter function itself. The methodology is based on the conventional coupling matrix technique for filter design and has been validated by fabricating a microstrip prototype using hairpin resonators and a rectangular patch antenna

Bilayer graphene under pressure: Electron-hole Symmetry Breaking, Valley Hall Effect, and Landau Levels

The electronic structure of bilayer graphene under pressure develops very interesting features with an enhancement of the trigonal warping and a splitting of the parabolic touching bands at the K point of the reciprocal space into four Dirac cones, one at K and three along the T symmetry lines. As pressure is increased, these cones separate in reciprocal space and in energy, breaking the electron-hole symmetry. Due to their energy separation, their opposite Berry curvature can be observed in valley Hall effect experiments and in the structure of the Landau levels. Based on the electronic structure obtained by Density Functional Theory, we develop a low energy Hamiltonian that describes the effects of pressure on measurable quantities such as the Hall conductivity and the Landau levels of the system.Comment: 11 pages, 9 figure

Nonlinear Performance of BAW Filters Including BST Capacitors

This paper evaluates the nonlinear effects occurring in a bulk acoustic wave (BAW) filter which includes barium strontium titanate (BST) capacitors to cancel the electrostatic capacitance of the BAW resonators. To do that we consider the nonlinear effects on the BAW resonators by use of a nonlinear Mason model. This model accounts for the distributed nonlinearities inherent in the materials forming the resonator. The whole filter is then implemented by properly connecting the resonators in a balanced configuration. Additional BST capacitors are included in the filter topology. The nonlinear behavior of the BST capacitors is also accounted in the overall nonlinear assessment. The whole circuit is then used to evaluate its nonlinear behavior. It is found that the nonlinear contribution arising from the ferroelectric nature of the BST capacitors makes it impractical to fulfill the linearity requirements of commercial filters

The influence of indol butyric-acid in Prunus laurocerasus L. vegetative propagation

Cherry laurel is very common as an ornamental plant, due to the large glossy leaves, fast growth, and shade and hedging tolerance. The influence of different indol-3- butiric acid (IBA) concentrations (1,000, 2,500, 5,000 and 7,500 ppm) was evaluated in early spring 2007. The data was gathered one month after bench cutting plantation. The parameters measured and analyzed were the number of rooted cuttings, the number of cuttings with callus formation and mortality, the mean number of roots (NR) and the mean main root length (MRL), per rooted cutting. The IBA application influenced the rooting percentage, the NR and the MRL, but the results were IBA concentration independent. In P. laurocerasus rooting ranged from 67% and 80%, when IBA was applied, values significantly superior to 37% of rooted cuttings in the control. The highest NR and MRL values were found in the treatment with 7,500 ppm IBA (27.2 of roots per cutting) and with 1,000 ppm IBA (MRL was 24.76 mm), respectively. Significantly lower values were obtained in the control: 5.56 NR and 9.4 mm of MRL. The IBA application significantly increased rooting, the NR and the MRL, with cuttings planted early in Spring, but the parameters were IBA concentration independent