From the past two decades, SiGe transistors have been identified as excellent candidates to match requirements both for high purity signal generation and high frequency applications. Moreover, SiGe BiCMOS technology takes benefit of CMOS devices that allow high integration levels for Monolithic Microwave Integrated Circuits (MMIC) Phase Locked Loop (PLL) systems. This work focuses on the only analog circuit of a PLL: the Voltage Controlled Oscillator (VCO) is one of the key stone of a transceiver, because its stability mainly influences the data rate of the channel. X-band and K-band VCOs are investigated. Design rules are thus compared for two different topologies in the X-band. K-band VCO is also designed to assess the technology behavior for higher frequencies. State of the art results are obtained and compared with the best published performances to date. New expressions of Figures Of Merit (FOM) are proposed to provide an accurate comparison between designs featuring scattered performances. IntroductionBiCMOS SiGe technologies offer great opportunities due to the high integration level with both analog and digital circuits operating at high frequencies, and also base-band modules matched to modern telecommunication systems' requirements. Moreover, the high performance (low noise, high operating frequency,…) associated with the relative low-cost gives advantage to such technologies in comparison with III-V foundries. The low frequency flicker noise (1/f) of SiGe Heteronjunction Bipolar Transistors (HBT) allows the design of MMIC voltage controlled oscillators (VCO) featuring excellent phase-noise: we present different VCO designs manufactured using the STMicroelectronics BiCMOS 0.35 µm and 0.25 µm processes for X-band and K-band applications.The paper is divided in three main sections. In the first part is presented a comparison between the reflection architecture (negative resistance) and the parallel feedback architecture operating in X-band. The second section presents the push-push differential oscillator in K-band. The last section proposes a comparison of this work with state of the art MMIC circuits: a new figure of merit (FOM) is introduced.

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Abstract. The structural design methods development nowadays allows including the effects of geometric and mechanical nonlinearity of the materials in the analysis itself. The resolution through matrixes methods frequently involves an incremental treatment for load application and a tangent stiffness matrix that bears in mind the nonlinearity. The present paper shows a procedure to evaluate the bar stiffness considering mechanical nonlinearity of materials. For structures of reinforced concrete formed by two materials where each of them has a resistant behavior so different from the other, its appropriated evaluation is, at the same time, necessary and especially complex. The iterative process exposed here provides the equilibrium position of the section to the general case of axial force and biaxial bending taking into account the nonlinear constituent relationships of materials. Once the equilibrium is reached, the relationship between the biaxial moment and the curvature allows the section stiffness module to be derived, from which the bar stiffness will be determined. As an application of the exposed procedure, the iterative process of the equilibrium research in a section of reinforced concrete is showed. At the moment-curvature diagram can be observed the stiffness progressive decreasing as biaxial bending moments are increasing, because of materials nonlinearity stresses and strains and the section inertia reduction produced by concrete cracking.

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Infectious mononucleosis (IM) is characterized by fever, swallowing pain (with or without pharyngeal exudate), neck adenopathies and, in characteristic cases, atypical lymphocytosis. Over 50% of all patients with IM present generally mild thrombocytopenia without clinical consequences, though in exceptional cases the condition may prove serious. Pseudothrombocytopenia (PT) is an in vitro artifact caused by antibody (generally IgG) -mediated platelet aggregation secondary to blood sample collection and processing in a medium containing ethylenediaminetetraacetic acid (EDTA). It can be associated to autoimmune disorders, drugs, solid tumors, and myeloproliferative and lymphoproliferative syndromes. We present a case of PT associated to IM in which the viral infection was the cause of false severe thrombopenia.