INESC-ID

About: INESC-ID is a nonprofit organization based out in Lisbon, Portugal. It is known for research contribution in the topics: Field-programmable gate array & Control theory. The organization has 932 authors who have published 2618 publications receiving 37658 citations.

Quadrature Van der Pol oscillators using second harmonic coupling

Abstract: A new coupling mechanism is used to synchronize two Van der Pol oscillators. This coupling uses the second harmonic appearing in common mode current of each oscillator. The common mode current is measured by a current mirror, and is amplified by a current amplifier. The amplifier introduces negative feedback, so that the current in the current mirror measuring diode of the first oscillator is nearly equal to the common mode current of the second oscillator, hence the coupling is established. It is shown that the system of two oscillators is described by two differential equations where the coefficients in one equation have the perturbations defined by the second oscillator, and vice versa. The coupling amplifier gain is defined. The developed concepts are demonstrated on a 5 GHz CMOS LC oscillator with quadrature outputs. The oscillator phase noise is lower than -116 dBc/Hz at 1-MHz offset.

Parallel Decimal Multipliers and Squarers Using Karatsuba-Ofman's Algorithm

Abstract: Financial and commercial applications depend on decimal arithmetic since the results must match exactly those obtained by human calculations. Multiplication and squaring are frequently used operations in these applications. In this paper we propose to improve the efficiency of state-of-the-art decimal multipliers using the Karatsuba-Ofman's algorithm. The method is also used to implement the squaring operation. The results indicate that the proposed parallel decimal multipliers based on the Karatsuba-Ofman's algorithm are very efficient with area reductions up to 30%. Also, the proposed decimal squarers achieve improvements in the area of almost 40% compared to a multiplier for the same number of digits, stressing the importance of dedicated implementations of these units

Integrated monitoring of infrastructures and applications in cloud environments

Abstract: One approach to fully exploit the potential of Cloud technologies consists in leveraging on the Autonomic Computing paradigm. It could be exploited in order to put in place reconfiguration strategies spanning the whole protocol stack, starting from the infrastructure and then going up to platform/application level protocols. On the other hand, the very base for the design and development of Cloud oriented Autonomic Managers is represented by monitoring sub-systems, able to provide audit data related to any layer within the stack. In this article we present the approach that has been taken while designing and implementing the monitoring sub-system for the Cloud-TM FP7 project, which is aimed at realizing a self-adapting, Cloud based middleware platform providing transactional data access to generic customer applications.

Efficient design of FIR filters using hybrid multiple constant multiplications on FPGA

Abstract: The multiple constant multiplication (MCM) block, which realizes the multiplication of constants by a variable, is a ubiquitous operation in digital signal processing (DSP) systems. It can be implemented using generic multipliers or shifts and adders/subtractors. This paper addresses the problem of finding the minimum number of adders/subtractors to realize the MCM block while a number of multipliers are available to realize some constant multiplications. Such a situation appears in the design of DSP systems on field programmable gate arrays (FPGAs) which also include generic multipliers. We present a 0-1 integer linear programming (ILP) formulation of this problem, yielding an exact common subexpression elimination (CSE) method. Due to the NP-completeness of this problem, we also introduce an approximate graph-based (GB) algorithm. Experimental results show that the proposed methods can find better solutions than a state-of-art algorithm and the use of different number of multipliers in the MCM block leads to filter designs with different number of slices, delay, and power dissipation which enable a designer to choose the one that fits best in an application.

On phase noise in quadrature cross-coupled oscillators

Abstract: A cross-coupled relaxation oscillator has two outputs of the same frequency, which are in quadrature. In this paper a comparative study of the phase noise in a cross-coupled relaxation oscillator is given. We present a high level (system) study of the oscillator and analyse the oscillator stability. The derivation proves analytically that cross-coupling reduces the influence of a perturbation (noise) on the oscillator output. Both high-level and circuit simulations at 5GHz are presented to confirm the theoretical results. Close to 10dB improvement in phase noise performance due to coupling was found, and the phase noise performance compared with that of a coupled LC oscillator was achieved.