Nikhil M. Kriplani

A Transient Electrothermal Analysis of Three-Dimensional Integrated Circuits

A transient electrothermal simulation of a 3-D integrated circuit (3DIC) is reported that uses dynamic modeling of the thermal network and hierarchical electrothermal simulation. This is a practical alternative to full transistor electrothermal simulations that are computationally prohibitive. Simulations are compared to measurements for a token-generating asynchronous 3DIC clocking at a maximum frequency of 1 GHz. The electrical network is based on computationally efficient electrothermal macromodels of standard and custom cells. These are linked in a physically consistent manner with a detailed thermal network extracted from an OpenAccess layout file. Coupled with model-order reduction techniques, hierarchical dynamic electrothermal simulation of large 3DICs is shown to be tractable, yielding spatial and temporal selected transistor-level thermal profiles.

Time-Domain Modelling of Phase Noise in an Oscillator

This paper presents a time-domain simulation of phase noise in a varactor-tuned voltage-controlled oscillator. Flicker, thermal and shot noise are captured using transient sources of noise based on the principles of mathematical chaos. High levels of noise are handled by replacing the ordinary differential equations used in conventional transient circuit simulation by stochastic differential equations. The system of stochastic differential equations is interpreted in the sense of Stratonovich. Simulation runs are compared with measured phase noise of the oscillator and an accurate match is found for different levels of bias

Why it is so hard to find small radio frequency signals in the presence of large signals

The essence of radar, radio and wireless sensor engineering is extracting small information-bearing signals. This is notoriously difficult and engineers compensate by transmitting high power signals, reducing range, and spacing wireless systems in frequency and time. New understandings of passive intermodulation distortion, thermal effects, time-frequency effects, and noise are presented. It is seen that the familiar frequency-domain-based abstractions have missed important underlying physics. Through greater understanding, RF engineers can develop microwave systems with far lower levels of distortion and noise.

Modelling of an Esaki Tunnel Diode in a Circuit Simulator

A method for circuit-level modelling a physically realistic Esaki tunnel diode model is presented. A paramaterisation technique that transforms the strongly nonlinear characteristic of a tunnel diode into two relatively modest nonlinear characteristics is demonstrated. The introduction of an intermediate state variable results in a physically realistic mathematical model that is not only moderately nonlinear and therefore robust, but also single-valued.

Streamlined Circuit Device Model Development with fREEDAR® ãnd ADOL-C

1 Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27695-7914. E-mail addresses for the NC State authors are, in order: fphart@eos.ncsu.edu, nmkripla@unity.ncsu.edu, srluniya@unity.ncsu.edu, and m.b.steer@ieee.org. 2 Department of Electrical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B 5E1, Canada. E-mail address: c.christoffersen@ieee.org.

Integration of FDTD EM analysis and transient circuit simulation of RF systems

A combined transient simulation of a 300 MHz input, 20 MHz output RF radio transceiver system was performed using an industry standard FDTD simulator integrated with an open source state-variable based multi-physics simulator. The two simulators were interfaced at every time step and several nonlinear iterations were performed at each step in order to ensure simulation convergence of the system which contains strong nonlinearities and a wide range of signal strengths at different points in the system.

fREEDA: An Open Source Circuit Simulator

fREEDAtrade is capable of transient, wavelet, harmonic balance, DC and AC analysis of circuits. Of these it is transient analysis has the greatest capability of revolutionizing the ability to design of RF circuits. fREEDAtrade uses a number of new strategies to achieve a dynamic range in transient simulation exceeding 160 dB, large signal noise analysis, modeling of oscillator phase noise, handling arbitrarily long time delays, and capturing mixed-physics. For the first time the overall philosophy behind fREEDAtrade is outlined with particular attention to topology

Fast dynamic simulation of VLSI circuits using reduced order compact macromodel of standard cells

This paper presents a dynamic simulation methodology using a reduced order compact macromodel of standard cells. The standard cell macromodels are formulated with a smaller number of state variables compared to an equivalent transistor-level implementation. This results in significant speed-ups over transistor-level simulation for large scale circuits. Such reduction in state variables also reduces memory usage. The macromodels are based on transistor equations, and simulation using these models produces results in excellent agreement (delay errors below 1%) with transistor-level simulation results. Various examples showing 1.5x−100x reduction in dynamic simulation time and 1.5x−2.8x reduction in memory usage are presented.