Mohamad El-Asmar

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An analytical design methodology of outphasing amplification systems is proposed using new simplified analytical expressions for the instantaneous efficiency and the input/output voltages of Chireix outphasing combiners. These expressions are derived first for ideal voltage sources with nonzero internal impedance and later for ideal Class-B amplifiers where(More)
In this paper, an analytic work is presented showing mathematically an approach where the impedance variation at the input of the Chireix combiner in function of the original phase is studied taking into account reflections between the combiner and the amplifiers. In order to prove that approach, two different experimental works are done. The first is done(More)
In this paper, we present the design and experimental characterization of an RF front-end suitable for automatic identification system (AIS) applications. The power amplifier (PA) is designed for class C operation at two output power level settings. The design procedure, including the choice of device, modeling for class C operation, stabilization and(More)
The efficiency and linearity of power amplifiers based on the LINC technique are discussed. The use of resistive combiners as well as lossless Chireix combiners are detailed and their impact on amplifier linearity and efficiency are highlighted. The tradeoffs between linearity and efficiency in Chireix combiners are investigated experimentally and optimal(More)
In this paper, we present the latest development and aspects regarding the mechanical as well as electrical modeling and design of shunt MEMS switches. The general equations of the spring constant, electrostatic voltage, quality factor and the damping coefficient are investigated in order to improve the time response of the membrane. Finally, a rapid shunt(More)
Different kinds of RF power combiner are studied. Wilkinson and hybrid combiner show very good linearity but low power efficiency. Chireix combiner using stubs at the input shows good efficiency and bad linearity of system. This paper shows that an unmatched chireix combiner without stub used at the output of class-B amplifiers can be optimized in(More)
In this paper, we present one more efficient LINC-outphasing power amplifier using a new model of Chireix combining system. In this model we use high response time MEMS (micro electro mechanical system) switches to connect and disconnect two different stubs at the input of the Chireix combiner. This exchange of two stubs is occurred at a fixed level of the(More)
This paper presents an investigation of the trade-offs between efficiency improvement and linearity of the outphasing power amplifier. Simulations and experimental measurements are carried out to validate the theoretical analysis. Two types of digital modulation signals are used, namely 16-QAM and 64-QAM. The impact of the stub length on the efficiency and(More)
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