51,118 research outputs found
Third-order Intermodulation Reduction in Mobile Power Amplifiers by the First Stage Bias Control
In this paper, the third order intermodulation distortion (IMD3) of three-stage power amplifier (PA) is analyzed using the Volterra series. The analysis explains how the total IMD3 of the three-stage power amplifier can be reduced by the first-stage bias condition. The three-stage PA, which is fabricated using InGaP/GaAs hetero-junction bipolar transistor (HBT), operates with an optimized first driver stage bias for higher P1dB and good gain flatness. The power amplifier has been designed for 1626.5 MHz~1660.5 MHz satellite mobile communications. With π/4 DQPSK modulation signals, this PA can deliver a highly linear output power of 33 dBm from 3.6V supply voltage. At 33 dBm output power, it shows a gain of 31.9 dB, a power-added efficiency (PAE) of 39.8%, an adjacent channel power ratio (ACPR) of -28.2 dBc at a 31.25 KHz offset frequency
Quark-Antiquark-Gluon Jets in DIS Diffractive Dissociation
We study the diffractive production of jets with large transverse
momenta in the region of large diffractive masses (small ). Cross
sections for transverse and longitudinal photons are obtained in the leading
log 1/x_{\fP} and log approximation, keeping all powers in log
. We perform a numerical study and illustrate the angular
distribution of the three jets. We also estimate the integrated diffractive
three jet cross section and compare with the dijet cross section obtained
before.Comment: 28 pages (Latex), 20 figures (Postscript
Massive c\bar c g - Calculation in Diffractive DIS and Diffractive D^* - Production at HERA
We calculate the cross section for -production in diffractive DIS
with finite quark masses at zero momentum transfer . The calculation is done
in the leading log(1/) approximation and is valid in the region of high
diffractive masses (small ). We apply our cross section formula
including both - and in a Monte Carlo simulation to
diffractive meson production at HERA. We compare our predictions to
results of H1 using three parameterizations for the unintegrated gluon density.Comment: 11 pages, 5 figure
Canonically Transformed Detectors Applied to the Classical Inverse Scattering Problem
The concept of measurement in classical scattering is interpreted as an
overlap of a particle packet with some area in phase space that describes the
detector. Considering that usually we record the passage of particles at some
point in space, a common detector is described e.g. for one-dimensional systems
as a narrow strip in phase space. We generalize this concept allowing this
strip to be transformed by some, possibly non-linear, canonical transformation,
introducing thus a canonically transformed detector. We show such detectors to
be useful in the context of the inverse scattering problem in situations where
recently discovered scattering echoes could not be seen without their help.
More relevant applications in quantum systems are suggested.Comment: 8 pages, 15 figures. Better figures can be found in the original
article, wich can be found in
http://www.sm.luth.se/~norbert/home_journal/electronic/v12s1.html Related
movies can be found in www.cicc.unam.mx/~mau
Theory of inter-edge superexchange in zigzag edge magnetism
A graphene nanoribbon with zigzag edges has a gapped magnetic ground state
with an antiferromagnetic inter-edge superexchange interaction. We present a
theory based on asymptotic properties of the Dirac-model ribbon wavefunction
which predicts and ribbon-width dependencies for the
superexchange interaction strength and the charge gap respectively. We find
that, unlike the case of conventional atomic scale superexchange, opposite
spin-orientations on opposite edges of the ribbon are favored by both kinetic
and interaction energies.Comment: 4 pages 8 figure
Magneto-electric coupling in zigzag graphene nanoribbons
Zigzag graphene nanoribbons can have magnetic ground states with
ferromagnetic, antiferromagnetic, or canted configurations, depending on
carrier density. We show that an electric field directed across the ribbon
alters the magnetic state, favoring antiferromagnetic configurations. This
property can be used to prepare ribbons with a prescribed spin-orientation on a
given edge.Comment: 4 pages, 5 figure
Direct comparison of the performance of CZT detectors contacted with various metals
Cadmium Zinc Telluride (CZT) achieves excellent spatial resolution and good
energy resolution over the broad energy range from several keV into the MeV
energy range. In this paper we present the results of a systematic study of the
performance of CZT detectors manufacturered by Orbotech (before IMARAD)
depending on surface preparation, contact materials and contact deposition. The
standard Orbotech detectors have the dimension of 2.0 x 2.0 x 0.5 cm. They have
a pixellated In anode with 8 x 8 pixels and a monolithic In cathode. Using the
same CZT substrates several times, we have made a direct comparison of the
performance of different contact materials by replacing the cathode and/or the
anode contacts with several high-workfunction metals. We present the
performance of the detectors and conclude with an overview over our ongoing
detector optimization.Comment: 8 pages, 5 figures, to appear in the proceedings of the conference
5922, "Hard X-Ray and Gamma-Ray Detector Physics VII" on the "Optics &
Photonics 2005" SPIE Symposium, July 31- August 4, 2005, San Diego, C
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