[Legacy Report] Physics-Based Approach of Nonlinear Noise Modelling For the Applications in Oscillators

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The conventional method to oscillator circuit design – which is currently important modules for modern communication system – is being traded simultaneously by an increase in operating frequencies, bandwidth and a decrease in physical footprint size. The result is that the physical design layout challenges faced by circuit designers are rapidly increasing, while choices for how these challenges should be best-addressed are kept
aside.
The oscillator design technology didn’t earn its reputation as black magic for no reason. Unlike other
microwave circuits, oscillators don’t behave in a totally predictable way, so “tweaking” has been an accepted mainstay of the signal sources design flow. Fortunately, high-frequency commercial design tools (Agilent ADS,Ansys, AWR Microwave Office, Cadence Design Systems SpectreRF, Avista Design Systems SP/XL-RF, etc.)have dramatically improved so that tweaking of prototype circuits is much less common, and today’s designers have powerful CAD tools that can make meaningful sense of the black magic.
However, progress in circuit simulation tools was not entirely paralleled in the development of device noise models, although the final result of the noise simulation is as good as the noise models implemented in the simulator. In frequency generating circuits, noise dynamics places stringent condition on these frequency sources owing to inherent high noise figure and low dynamic range caused by the uncontrolled nonlinearity at large-signal drive-level conditions. In addition, these problems become critical at high frequency when active devices (Bipolars/FETs) are technologically scaled to obtain higher cut-off frequency.
The objective of this talk is to provide a brief review of physics-based noise analysis using Green’s function to evaluate the second-order statistical properties of the device noise generators (including their correlation) from the elementary, microscopic fluctuations (the microscopic noise sources) occurring within the device volume, given the noiseless working point of the device. The microscopic noise sources, assumed to be known from physical first principles, can be associated with three phenomenon: fluctuations of the velocity of free carriers(leading to diffusion noise which, in thermal equilibrium, corresponds to thermal noise), fluctuations of the number of free carriers (leading to GR noise), and 1/f noise. Unfortunately, the physical origin of 1/f noise is still an open issue; several competing theories have been proposed, but experimental verifications have shown controversial results. The physics-based approach of nonlinear noise modeling can offer unified solution to many noise modeling problems encountered in RF and microwave circuit design, especially oscillators,frequency multipliers, and mixers.
Dr. Ajay K. Poddar graduated from IIT Delhi, Ph.D. from TU-Berlin (Technical University Berlin) Germany.Dr. Poddar is a Chief Scientist, responsible for design and development of state-of-the-art technology(oscillator, mixer, amplifier, filters, and MEMS based RF components) at Synergy Microwave Corporation NJ,USA. He also holds the position of guest professor at Technical University Munich, Germany. Previously, he worked as a Senior Scientist in DRDO (Defense Research and Development Organization) (1991-2001), India. Dr. Poddar holds 42 US and European patents and has published more than 180 scientific papers in international conferences and professional journals, contributed as a coauthor of 5 technical books. Dr. Poddar is a recipients of three time DRDO young scientist awards (1997, 1999, 2000), and IEEE USA Outstanding research scientist award (2009). Dr. Poddar is a senior member of professional societies IEEE (USA), AMIE (India), and IE(India) and involved in academic review committee (India and Abroad), Academic Advisory Board (India and Abroad), and PhD Advisors.

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