Low energy design techniques for digital circuits are examined to determine their suitability for use in a digital logic controller for wireless sensor network nodes. Transistor level simulations are used to evaluate the techniques and those demonstrating an energy reduction are used to implement a digital logic controller. The digital...
In this thesis, the performance degradation of a phase-locked loop due to substrate noise is examined. A new analytical equivalent circuit model for substrate noise coupling is derived for a heavily doped silicon substrate. The model has been validated with measured data from a 0.35 μm CMOS process. Since the...
A scalable macromodel for substrate noise coupling in lightly doped substrates with and without a buried layer has been developed. This model is based on Z-parameters and is scalable with contact size and separation. This model requires process dependent parameters that can be extracted easily from a small number of...
The focus of this work is on the steady-state analysis of RE circuits using a coupled device and circuit simulator. Efficient coupling algorithms for both the time-domain shooting method and the frequency-domain harmonic balance method have been developed. A modified Newton shooting method considerably improves the efficiency and reliability of...
Strategies for simulation and measurement of substrate noise have been analyzed using various digital and analog circuits fabricated in the TSMC 0.35um heavily doped CMOS process. The measurements validate a substrate noise coupling macromodel that has been used to obtain the simulation results. The simulations and measurements also substantiate the...
Efficient methods for simulating the substrate noise generated by complex synchronous and asynchronous digital logic circuits are presented. By simulating digital logic at the gate level, and precharacterizing the gates, the substrate noise generation can be predicted and used in a transistor level simulation of the sensitive analog blocks. This...
This thesis presents Silencer!, a fully automated, schematic-driven tool for substrate noise coupling simulation and analysis. It has been integrated in the CADENCE DFII environment and seamlessly enables substrate coupling analysis in a standard mixed-signal design flow. Silencer! aids IC designers in the analysis of substrate noise coupling at different...
This thesis presents an automated methodology to calibrate the substrate profile for accurate prediction of substrate parasitics using Green's function based extractors. The technique requires fabrication of only a few test structures and results in an accurate three layered approximation of a heavily doped epitaxial silicon substrate. The obtained substrate...
This thesis presents distinctly different methods of accurately predicting phase noise and absolute jitter in ring oscillators. The phase noise prediction methods are the commercially available SpectreRF and isf_tool, a simulator developed in this work from the Hajimiri and Lee theory of phase noise. Absolute jitter due to deterministic supply...
Circuits operating outside the earth’s atmosphere are more vulnerable to cosmic radiation and require special design consideration. The purpose of this work is to explore methods of mitigating the effect of radiation in phase locked loop (PLL) circuits. Several voltage controlled oscillators (VCOs) and two complete PLLs are designed and...
This work focusses on the modeling and the development of efficient coupled simulation techniques for MEMS based RF oscillators. High-level models for MEMS based varactors have been discussed and their accuracy issues are identified, based on comparisons with numerical simulations. A faster simulation approach based on the time-domain shooting method...
The dependence of the substrate resistance, R[subscript sub], for MOS transistor RF modeling on transistor biasing and layout is studied from device simulations and measurements. Though R[subscript sub] is found to be bias dependent, the error incurred by assuming a constant value equal to the DC resistance is not significant....
The substrate noise injected by a stepped buffer circuit into two single-ended 1.5GHz low noise amplifiers is examined for a heavily doped 0.25µm CMOS process. The difference in the LNA noise rejection is characterized as a function of the size and placement of substrate contacts. The use of a resistive...
The focus of this work is on developing algorithms for frequency domain steady-state analysis of oscillators. Convergence problems associated with the frequency domain harmonic balance simulation of oscillators have been examined. Globally convergent homotopy methods have been combined with the harmonic balance method for robust high-Q oscillator simulation. Various homotopy...
As the demand for real-time information in engineering and health care systems keeps increasing, the need for wireless sensor nodes is also continuously increasing. As a result, the cost and effort involved in installing and maintaining batteries to power the numerous sensor nodes is growing exponentially. Providing a cost effective...
A digital implementation of a PLL has several advantages compared to its
analog counterpart. These include easy scalability with process shrink, elimination
of the noise susceptible analog control for a voltage controlled oscillator (VCO) and
the inherent noise immunity of digital circuits. Several recent digital PLL (DPLL)
implementations have achieved...
Spacecrafts experience radiation in the course of their operation
and all electronic equipment on board these spacecrafts has to
be designed to withstand the effects of this radiation.
This thesis describes the effects of total ionization dose (TID)
and single event transients (SET) in phase-locked loops - an
important circuit...
The continued scaling of deep-submicron CMOS technology enables low-voltage high-frequency phase-locked loops (PLLs) to be fully integrated in complex mixed-signal systems. However, fluctuations due to the manufacturing process and variations in
environmental conditions, such as supply voltage and temperature, are also significantly increased. As a result, the performance of PLLs...
A new coupled circuit and electrostatic/mechanical simulator (COSMO) for the design of RF MEMS VCOs is presented in this thesis. The numerical solution of device level equations is used to accurately compute the capacitance of a MEMS capacitor. This coupled with a circuit simulator facilitates the simulation of circuits incorporating...
This thesis presents the contributions to substrate noise due to supply coupling and the effect of pin parasitics on the substrate noise generated by digital circuits. Various sources of substrate noise and their effect on analog circuits sharing the same substrate are discussed. A simulation approach to isolate the various...
A Z-parameter based macromodel for characterizing the substrate noise coupling in a lightly doped substrate at low frequencies has been developed. The model is scalable with contact geometries and separation. The cross-coupling impedance between two contacts is modeled using an improved geometric mean distance formulation. This approach obviates the need...
This thesis presents a comparison of time-domain and frequency-domain algorithms for phase noise calculation in oscillators. Floquet theory provides the mathematical foundation for these calculations and the numerical methods employ perturbation projection vectors (PPVs). The PPVs are an estimate of an oscillator's sensitivity to noise.
The in-house circuit simulator SPICE3...
Delay insensitive asynchronous circuitry provides significant advantages with
respect to substrate noise due to localized switching. The differences between the
substrate noise from NULL Convention Logic (NCL) and traditional Clocked
Boolean Logic (CBL) are described and analyzed based on measured results. A test chip fabricated in the TSMC 0.25 um...
Low noise oscillators are universally needed in digital systems for clock generation and synchronization, and in radio-frequency communication front-ends for frequency up- and down-conversion. Noise in oscillators results in timing jitter, and limits the clock frequency of digital systems. In radio-frequency communication systems, phase noise in oscillators lowers the signal-to-noise...
This thesis examines substrate noise coupling for NMOS transistors in heavily doped substrates. The study begins with the analysis of an NMOS transistor switching noise in a digital inverter at the device level. A resistive substrate network for the NMOS transistor is proposed and verified. Coupling between N+- P+ contacts...
An analysis that accounts for the effect of standard electrostatic discharge (ESD) structures on critical LNA specifications of noise figure, input matching and gain is presented. It is shown that the ESD structures degrade LNA performance particularly for higher frequency applications. Two LNAs, one with ESD protection and one without,...
A fully integrated CMOS GPS receiver RF front end optimized for low power operation is presented. The system operates with a supply voltage down to 250 mV. A prototype has been fabricated in a 0.13μm CMOS process and includes a low voltage LNA, quadrature oscillators, and quadrature mixers. It exhibits...
An ultra low power crystal oscillator that provides a frequency reference for battery
powered timekeeping applications is presented. An amplitude control circuit is employed to ensure that minimum current is consumed. A subthreshold voltage regulator provides a supply voltage for the oscillator with minimum current consumption. The oscillator and regulator...
An enhanced swing differential Colpitts VCO (ESDC-VCO) dramatically improves
the swing of a Colpitts VCO by allowing the signal to swing below ground and above the
supply voltage. Fabricated in a 1P8M 0.13 um CMOS process, the ESDC-VCO operates
at 4.9GHz with a 0.475-V supply and consumes 2.7mW. The measured...
This thesis presents a Z-parameter based model to predict the substratenoise coupling between two contacts in a heavily doped substrate for frequenciesless than 2 GHz. The empirical model is scalable with contact size and spacingsbetween the contacts and model parameters can be readily extracted from simu-lated or measured data. The...
This thesis presents algorithms and tools for the automated design of RF LC CMOS voltage controlled oscillators (VCOs) with low phase noise given a set of specifications. The electromagnetic solver, ASITIC, combined with the circuit simulator, SpectreRF, allows optimization of the VCO circuit parameters and inductor layout. This approach gives...
Algorithms and simulators comprised of SPICE3 as a circuit level simulator and two device simulators EOFLOW and PROPHET for accurate simulation of new types of devices are presented in this thesis. An integration of EOFLOW with SPICE3 creates a capability for efficient simulation of a system containing interconnected electroosmotic flow...
A new method is presented to compress switching information in large digital circuits. This is combined with an efficient approach of generating the noise signatures of cells in a digital library that results in an accurate and efficient approach for estimating the noise generated in digital circuits. This method provides...
At frequencies exceeding 1-2 GHz, the substrate network models used in substrate coupling simulation must account for the reactive nature of the substrate. Unlike at low frequencies, where the purely resistive substrate models can be validated through DC resistance measurements, these high-frequency models, comprising reactive components, must be validated through...
This thesis presents a design-oriented model for lightly doped CMOS substrates. The model predicts the substrate noise coupling between noisy digital and sensitive analog blocks in the early stages of the design. The model scales with the size and separation of these blocks and it is validated with device simulations...
Digital phase-locked loops (PLLs) have been receiving increasing attention recently due to their ease of integration, scalability and performance comparable to their analog counterparts. In digital PLLs, increased resolution in time-to-digital conversion is desirable for improved noise performance. This work describes the design and simulation of a stochastic time-to-digital converter...
A fully integrated CMOS latched comparator is presented for use as a wake-up circuit that is attached to an RF energy harvester in a battery free wireless sensor network. The system consumes less than 36nA static current at 20°C and dissipates 2pJ of energy per conversion. The comparator comprises of...
A methodology for rapid estimation of substrate noise generated by digital circuitry in mixed-signal circuits is presented. This methodology is incorporated into the Silencer! framework, and also provides for future improvements including pre-layout noise estimation. Measurements of a test chip fabricated in the TSMC o.25[mu]m heavily doped logic process validate...
Three types of low noise amplifiers operating at 2.4GHz were designed. They are the commonly used single-ended and differential amplifiers as well as a new quasi-differential amplifier. The substrate noise injected into these amplifiers is examined for both heavily and lightly doped CMOS substrates. For the single-ended amplifier the noise...
An analysis of substrate noise coupling in mixed-signal circuits has been performed in the TSMC 0.25 [mu]m lightly doped and heavily doped CMOS processes. Methods to minimize noise coupling in both the chip design and board design phases are presented along with techniques for accurate circuit simulation of noise coupling....