Noise investigations are firstly performed at the device level (transistor, diode…), and particularly on small devices dedicated to high frequency applications (sub-micron transistors and other nano-scale devices). These devices, because of the reduction in size, feature generally a relatively high level of 1/f noise, which must be considered for applications.
Low frequency noise measurement in a shielded room
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The noise investigations are also performed in order to check the reliability of a given device. Indeed, the noise is very sensitive to any change in the device microscopic structure, and can detect a defect or the growing of a defect much before other electrical parameters. Together with physical modelling, this approach allows us to assess the reliability in recently developed transistors (GaN, SiGe…) and to understand the origin of the observed shortcomings.
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All these studies are not only dedicated to the devices improvement, but also lead to enhanced circuit and system modelling. The devices modelled with their noise sources are embedded in the circuit, and the overall noise can be accurately predicted using linear or nonlinear CAD techniques.
Such a methodology is used for microwave non-linear circuits and systems modelling and design. A large amount of work has been performed particularly to model the phase noise in oscillators, and more generally, in microwave sources (synchronized oscillators…). Today, this approach is extended to various non-linear circuits and systems, with the aim of describing the noise behaviour of complex systems, including analogue and digital sub-circuits. |
High frequency noise measurement (1-40 Ghz)
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