Pierluigi Nuzzo

An 820μW 9b 40MS/s Noise-Tolerant Dynamic-SAR ADC in 90nm Digital CMOS

Current trends in analog/mixed-signal design for battery-powered devices demand the adoption of cheap and power-efficient ADCs. SAR architectures have been recently demonstrated as able to achieve high power efficiency in the moderate-resolution/medium- bandwidth range in Craninckx, J. and Van der Plas, G., (2007). However, when the comparator determines in first instance the overall performance, as in most SAR ADCs, comparator thermal noise can limit the maximum achievable resolution. More than 1 and 2 ENOB reductions are observed in Craninckx, J. and Van der Plas, G., (2007) and Kuttner, F., (2002), respectively, because of thermal noise, and degradations could be even worse with scaled supply voltages and the extensive use of dynamic regenerative latches without pre-amplification. Unlike mismatch, random noise cannot be compensated by calibration and would finally demand a quadratic increase in power consumption unless alternative circuit techniques are devised.

A 2-mm

A software-defined radio (SDR) should theoretically receive any modulated frequency channel in the (un)licensed spectrum, and guarantee top performance with energy savings, while still being integrated in a digital CMOS technology. This paper demonstrates a practical 0.1-5 GHz front-end implementation for such an SDR concept, including receiver and local oscillator (LO), with only 2-mm2 core area occupation in a 45-nm CMOS process. This scalable radio uses shunt-shunt feedback LNAs, a passive mixer with enhanced out-of-band IIP3, and a fifth order low-area 0.5-20 MHz baseband filter. LO quadrature signals are generated from a dual-VCO 4-10 GHz fractional-N PLL. With noise figure between 2.3 dB and 6.5 dB, out-of-band IIP3 between -3 dBm and -10 dBm, and total power consumption between 59 and 115 mW from a 1.1-V supply voltage, the presented prototype favorably compares with state-of-the-art dedicated radios while enabling, for the first time, wideband reconfigurable performance and energy scalability.

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In an aircraft electric power system, one or more supervisory control units actuate a set of electromechanical switches to dynamically distribute power from generators to loads, while satisfying safety, reliability, and real-time performance requirements. To reduce expensive redesign steps, this control problem is generally addressed by minor incremental changes on top of consolidated solutions. A more systematic approach is hindered by a lack of rigorous design methodologies that allow estimating the impact of earlier design decisions on the final implementation. To achieve an optimal implementation that satisfies a set of requirements, we propose a platform-based methodology for electric power system design, which enables independent implementation of system topology (i.e., interconnection among elements) and control protocol by using a compositional approach. In our flow, design space exploration is carried out as a sequence of refinement steps from the initial specification toward a final implementation by mapping higher level behavioral and performance models into a set of either existing or virtual library components at the lower level of abstraction. Specifications are first expressed using the formalisms of linear temporal logic, signal temporal logic, and arithmetic constraints on Boolean variables. To reason about different requirements, we use specialized analysis and synthesis frameworks and formulate assume guarantee contracts at the articulation points in the design flow. We show the effectiveness of our approach on a proof-of-concept electric power system design.

0.1–5 GHz Software-Defined Radio Receiver in 45-nm Digital CMOS

We introduce a platform-based design methodology that uses contracts to specify and abstract the components of a cyber-physical system (CPS), and provide formal support to the entire CPS design flow. The design is carried out as a sequence of refinement steps from a high-level specification to an implementation built out of a library of components at the lower level. We review formalisms and tools that can be used to specify, analyze, or synthesize the design at different levels of abstraction. For each level, we highlight how the contract operations can be concretely computed as well as the research challenges that should be faced to fully implement them. We illustrate our approach on the design of embedded controllers for aircraft electric power distribution systems.

A Contract-Based Methodology for Aircraft Electric Power System Design

A threshold configuring SAR A/D converter is presented that programs its comparator threshold at runtime to approximate the input signal via binary search. Low power and small area are achieved via a fully dynamic configurable comparator and an asynchronous controller with no need for capacitor-based feedback D/A converter. A 6-bit prototype in 90-nm digital CMOS technology achieves 32-dB SNDR at 50 MS/s consuming 240 μW from 1-V analog and 0.7-V digital supplies, i.e. 150fJ/conversion-step, in a core area occupation of only 0.0055 mm2, a 4× improvement on state-of-the-art designs.

A Platform-Based Design Methodology With Contracts and Related Tools for the Design of Cyber-Physical Systems

The requirements of next-generation wireless terminals are driving RFIC design toward ubiquitous multistandard connectivity at reduced power consumption and cost [1–3]. While the use of scaled CMOS technology is required to allow economically feasible single-chip integration with a digital processor, a Software-Defined Radio (SDR) is the preferred approach to provide a reconfigurable platform, that covers a broad range of noise/linearity specifications while offering the best power/performance trade-off [4,5].

A 6-Bit 50-MS/s Threshold Configuring SAR ADC in 90-nm Digital CMOS

Secure state estimation is the problem of estimating the state of a dynamical system from a set of noisy and adversarially corrupted measurements. Intrinsically a combinatorial problem, secure state estimation has been traditionally addressed either by brute force search, suffering from scalability issues, or via convex relaxations, using algorithms that can terminate in polynomial time but are not necessarily sound. In this paper, we present a novel algorithm that uses a satisfiability modulo theory approach to harness the complexity of secure state estimation. We leverage results from formal methods over real numbers to provide guarantees on the soundness and completeness of our algorithm. Moreover, we discuss its scalability properties, by providing upper bounds on the runtime performance. Numerical simulations support our arguments by showing an order of magnitude decrease in execution time with respect to alternative techniques. Finally, the effectiveness of the proposed algorithm is demonstrated by applying it to the problem of controlling an unmanned ground vehicle.

A 2mm 2 0.1-to-5GHz SDR receiver in 45nm digital CMOS

The design of complex analog interfaces would largely benefit from model-based development and compositional methods to improve the quality of its final result. However, analog circuit behaviors are so tightly intertwined with their environment that: 1) abstractions needed for model-based design are often not accurate, thus making it difficult to achieve reliable system performance estimations, and 2) generic, design-independent interfaces that are needed to develop compositional techniques are very difficult to define. In this paper, we propose a platform-based design methodology that uses analog contracts to develop reliable abstractions and design-independent interfaces. A contract explicitly handles pairs of properties, representing the assumptions on the environment and the promises of a component under these assumptions. Horizontal contracts encode composition rules that constrain how library elements should be “legally” used. Vertical contracts define under which conditions an aggregation of components satisfies the requirements posed at a higher level of abstraction. If both sets of contracts are satisfied, we can produce implementations by composition and refinement that are correct by construction. We demonstrate the effectiveness of this approach on the design of an ultra-wide band receiver used in an Intelligent Tire system, an on-vehicle wireless sensor network for active safety applications.

Secure State Estimation for Cyber-Physical Systems Under Sensor Attacks: A Satisfiability Modulo Theory Approach

We address the problem of detecting and mitigating the effect of malicious attacks on the sensors of a linear dynamical system. We develop a novel, efficient algorithm that uses a Satisfiability Modulo Theory approach to isolate the compromised sensors and estimate the system state despite the presence of the attack, thus harnessing the intrinsic combinatorial complexity of the problem. Simulation results show that our algorithm compares favorably with alternative techniques, with respect to both runtime and estimation error.

Methodology for the Design of Analog Integrated Interfaces Using Contracts

Aircraft Electric Power Systems (EPS) route power from generators to vital avionic loads by configuring a set of electronic control switches denoted as contactors. In this paper, we address the problem of designing a hierarchical optimal control strategy for the EPS contactors in the presence of system faults. We first formalize the system connectivity, safety and performance requirements in terms of mathematical constraints. We then show that the EPS control problem can be formulated as a Mixed-Integer Linear Program (MILP) and efficiently solved to yield load shedding, source allocation, contactor switching and battery charging policies, while optimizing a number of performance metrics, such as the number of used generators and shed loads. This solution is then integrated into a hierarchical control scheme consisting of two layers of controllers. The high-level controller provides control optimality by solving the MILP within a receding horizon approach. The low-level controller handles system faults, by directly actuating the EPS contactors, and implements the solution from the high-level controller only if it is safe. Simulation results confirm the effectiveness of the proposed approach.