26,743 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
Multi-user lattice coding for the multiple-access relay channel
This paper considers the multi-antenna multiple access relay channel (MARC),
in which multiple users transmit messages to a common destination with the
assistance of a relay. In a variety of MARC settings, the dynamic decode and
forward (DDF) protocol is very useful due to its outstanding rate performance.
However, the lack of good structured codebooks so far hinders practical
applications of DDF for MARC. In this work, two classes of structured MARC
codes are proposed: 1) one-to-one relay-mapper aided multiuser lattice coding
(O-MLC), and 2) modulo-sum relay-mapper aided multiuser lattice coding
(MS-MLC). The former enjoys better rate performance, while the latter provides
more flexibility to tradeoff between the complexity of the relay mapper and the
rate performance. It is shown that, in order to approach the rate performance
achievable by an unstructured codebook with maximum-likelihood decoding, it is
crucial to use a new K-stage coset decoder for structured O-MLC, instead of the
one-stage decoder proposed in previous works. However, if O-MLC is decoded with
the one-stage decoder only, it can still achieve the optimal DDF
diversity-multiplexing gain tradeoff in the high signal-to-noise ratio regime.
As for MS-MLC, its rate performance can approach that of the O-MLC by
increasing the complexity of the modulo-sum relay-mapper. Finally, for
practical implementations of both O-MLC and MS-MLC, practical short length
lattice codes with linear mappers are designed, which facilitate efficient
lattice decoding. Simulation results show that the proposed coding schemes
outperform existing schemes in terms of outage probabilities in a variety of
channel settings.Comment: 32 pages, 5 figure
Having Second Thoughts? Let's hear it
Deep learning models loosely mimic bottom-up signal pathways from low-order
sensory areas to high-order cognitive areas. After training, DL models can
outperform humans on some domain-specific tasks, but their decision-making
process has been known to be easily disrupted. Since the human brain consists
of multiple functional areas highly connected to one another and relies on
intricate interplays between bottom-up and top-down (from high-order to
low-order areas) processing, we hypothesize that incorporating top-down signal
processing may make DL models more robust. To address this hypothesis, we
propose a certification process mimicking selective attention and test if it
could make DL models more robust. Our empirical evaluations suggest that this
newly proposed certification can improve DL models' accuracy and help us build
safety measures to alleviate their vulnerabilities with both artificial and
natural adversarial examples.Comment: 13 pages, 11 figures, 1 table, 2 supplementary tables and 1
supplementary figur
Eccomi pronto : implementation of a Socio-Emotional Development curriculum in a South Korean elementary school
‘Eccomi Pronto’ (EP), an elementary school socio-emotional learning curriculum that
was originally developed and evaluated in Italy was translated in Korean and
implemented and evaluated in 4th grade classrooms of a primary school in South Korea.
Qualitative data from teachers indicated that EP improved the self-reflection and selfdirection
of students, resulted in pedagogically useful insights into the psychological
functioning of students, and enhanced the quality of teacher-student interaction.
However, statistically significant changes in students’ engaged, academic behavior (as
measured by an 8-item survey) were not noted. Teachers reported that the core of the EP
curriculum was appropriate for the South Korean educational context. Teachers also
recommended modifications in the follow-up learning activities to make these activities
more consistent with South Korean education practices.peer-reviewe
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