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

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

New heat treatment to prepare high quality polycrystalline and single crystal MgB2 in single process

We report here on a new heat treatment to prepare both dense polycrystalline and single crystal MgB2 high quality samples in one single process. Resistivity measurements for polycrystalline part of the sample gives a residual resistivity ratio RRR=16.6 and a very low normal state resistivity rho(40K)= 0.28 microOhmcm. Both SEM and SQUID study on polycrystals reveal the high quality, dense character and well coupling of grain boundaries. On the other hand, the high quality single crystals have a unique shape that resembles the hexagonal crystal structure. SQUID measurements reveals very weak flux pinning character implying our single crystals to be very clean. In this study, we conclude that heat treatment is playing a major rule on the characteristics of both polycrystalline and single crystal MgB2. Samples are thoroughly characterized by x-ray, resistivity, dc SQUID and SEM