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This paper gives an overview of several design issues for CMOS Power Amplifiers (PA) for wireless and mobile communications. The challenges, faced by the RF PA designer, and the different trade-offs, encountered during the design process, are clearly indicated. The idea of power combining is introduced and it is clarified how this technique can alleviate some of the problems related to the aggressive CMOS scaling. The theory is clarified by several design examples that cover a frequency range from the lower GHz as high as 60 GHz. [ABSTRACT FROM AUTHOR]

Many insects like, for example, ants communicate via chemical signals. This process, called chemotaxis, allows them to build large trail systems which have many similarities with human transport networks. In order to investigate the dynamics and spatio-temporal organization of ants on an existing trail system we have proposed a stochastic cellular automaton model. In contrast to the situation in highway traffic, it predicts a non-monotonic speed-density relation. This effect has its origin in the formation of loose clusters, i.e. space regions of enhanced, but not maximal, density. Inspired by the behaviour of ants on their trails, we have also developed a model for pedestrian dynamics. In this approach the interaction between the pedestrians is implemented as "virtual chemotaxis". In this way all interactions are strictly local and so even large crowds can be simulated very efficiently. In addition, the model is able to reproduce the empirically observed collective effects, e.g. the formation of lanes in counterflow. [ABSTRACT FROM AUTHOR]

We generalize cellular automaton models for uni-directional ant-trails to bi-directional motion. Several extensions (1-lane, 2-lane with and without common pheromone trail) corresponding to different realistic situations are compared. The interactions between the ants give rise to interesting collective behavior which is reflected in the flow properties and the spatio-temporal organization of the ants along the trail. [ABSTRACT FROM AUTHOR]

Many insects like ants communicate chemically via chemotaxis. This allows them to build large trail systems which in many respects are similar to human-build highway networks. Using a stochastic cellular automaton model we discuss the basic properties of the traffic flow on existing trails. Surprisingly it is found that in certain regimes the average speed of the ants can vary non-monotonically with their density. This is in sharp contrast to highway traffic. The observations can be understood by the formation of loose clusters, i.e. space regions of enhanced, but not maximal, density. We also discuss the effect of counterflow on the trails. [ABSTRACT FROM AUTHOR]