34,056 research outputs found

    A general theory of phase noise in electrical oscillators

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    A general model is introduced which is capable of making accurate, quantitative predictions about the phase noise of different types of electrical oscillators by acknowledging the true periodically time-varying nature of all oscillators. This new approach also elucidates several previously unknown design criteria for reducing close-in phase noise by identifying the mechanisms by which intrinsic device noise and external noise sources contribute to the total phase noise. In particular, it explains the details of how 1/f noise in a device upconverts into close-in phase noise and identifies methods to suppress this upconversion. The theory also naturally accommodates cyclostationary noise sources, leading to additional important design insights. The model reduces to previously available phase noise models as special cases. Excellent agreement among theory, simulations, and measurements is observed

    Oscillator phase noise: a tutorial

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    Linear time-invariant (LTI) phase noise theories provide important qualitative design insights but are limited in their quantitative predictive power. Part of the difficulty is that device noise undergoes multiple frequency translations to become oscillator phase noise. A quantitative understanding of this process requires abandoning the principle of time invariance assumed in most older theories of phase noise. Fortunately, the noise-to-phase transfer function of oscillators is still linear, despite the existence of the nonlinearities necessary for amplitude stabilization. In addition to providing a quantitative reconciliation between theory and measurement, the time-varying phase noise model presented in this tutorial identifies the importance of symmetry in suppressing the upconversion of 1/f noise into close-in phase noise, and provides an explicit appreciation of cyclostationary effects and AM-PM conversion. These insights allow a reinterpretation of why the Colpitts oscillator exhibits good performance, and suggest new oscillator topologies. Tuned LC and ring oscillator circuit examples are presented to reinforce the theoretical considerations developed. Simulation issues and the accommodation of amplitude noise are considered in appendixes

    Design issues in CMOS differential LC oscillators

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    An analysis of phase noise in differential cross-coupled inductance-capacitance (LC) oscillators is presented. The effect of tail current and tank power dissipation on the voltage amplitude is shown. Various noise sources in the complementary cross-coupled pair are identified, and their effect on phase noise is analyzed. The predictions are in good agreement with measurements over a large range of tail currents and supply voltages. A 1.8 GHz LC oscillator with a phase noise of -121 dBc/Hz at 600 kHz is demonstrated, dissipating 6 mW of power using on-chip spiral inductors

    Democratic Development and the Role of Citizenship Education in Sub-Saharan African with a Case Focus on Zambia

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    In addressing issues related to problems of democratisation in Africa, this paper attempts to relate the issue to the need for citizenship education and the role that can play in social development. Citizenship should be central to the formation of viable civil societies that claim a tangible stake in national public spaces in post-Cold War Africa. These and related topics are discussed relative to new possibilities that could lead to the full realisation of the concept as well as the practice of enfranchised citizenship and inclusive social development in aspiring democracies in the Sub Saharan African context. The complexity of the development ‘problematique’ that Sub-Saharan Africa is facing is unique in that it is multi-dimensional, but above all else, politically located. It is, therefore, central to our discussions here that to correct the continent’s current schemes of underdevelopment, pragmatic schemes of governance must be achieved. To do that, we are suggesting, new possibilities of citizenship education should be formulated for the general African scene in general, and for democratising but still both institutionally and economically weakened Zambia

    Gauge invariant generalization of the 2D chiral Gross-Neveu model

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    By means of the Lee-Shrock transformation we generalize the 2D Gross-Neveu (GN2_2) model to a U(1) gauge theory with charged fermion and scalar fields in 2D (χUϕ2\chi U \phi_2 model). The χUϕ2\chi U \phi_2 model is equivalent to the GN2_2 model at infinite gauge coupling. We show that the dynamical fermion mass generation and asymptotic freedom in the effective four-fermion coupling persist also when the gauge coupling decreases. These phenomena are not influenced by the XY2_2 model phase transition at weak coupling. This suggests that the χUϕ2\chi U \phi_2 model is in the same universality class as the GN2_2 model and thus renormalizable.Comment: Contribution to Lattice 95, LaTeX file (4 pages), 4 ps-figures appended (uuencoded), abstract correcte
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