J. Chavez

FASY: a fuzzy-logic based tool for analog synthesis

A CAD tool for analog circuit synthesis is presented. This tool, called FASY, uses fuzzy-logic based reasoning to select one topology among a fixed set of alternatives. For the selected topology, a two-phase optimizer sizes all elements to satisfy the performance constraints minimizing a cost function. In FASY, the decision rules used in the topology selection process are introduced by an expert designer or automatically generated by means of a learning process that uses the optimizer mentioned above. The capability of learning topology selection rules by experience, is unique in FASY. Practical examples demonstrate the tool ability of this tool to learn topology selection rules and to synthesize analog cells with different circuit topologies.

Analog design optimization by means of a Tabu Search approach

Although many design tools have been developed for digital design, analog design tools are just being introduced. This paper deals with device sizing of analog cells. A new method using the Tabu Search heuristic is proposed. It minimizes a given cost function, which depends on a set of designer specifications. The results obtained show that this method can approach very close the global minimum of the cost function with only a few number of iterations. Hence, an analog simulation program, such as SPICE, can be used for the evaluation of the cost function at each iteration.<<ETX>>

Circuit performance modeling by means of fuzzy logic

This paper presents a fuzzy-logic based approach to circuit performance modeling. Starting from a set of input-output vectors obtained by simulation (the training set), an automatic process adapts model parameters by means of neurofuzzy techniques. The resulting model can accurately reproduce the training set, even for a moderate number of rules. The results obtained in several analog and digital examples, show that accurate models can be obtained with a simple, completely automatic process. To demonstrate the usefulness of the proposed model, it is used to evaluate the circuit performances in the optimization process of an analog cell, achieving considerable speed-up.

Fuzzy-logic-based analog design tools

We have developed a collection of tools for the design, modeling, and test of analog circuits. Sharing a common fuzzy-logic based framework, the tools are part of FASY (Fuzzy-Logic-Based Analog Synthesis), an analog design package developed at the University of Seville. The first tool uses fuzzy logic for topology selection of analog cells. It follows decision rules directly entered by a human expert or automatically generated from its experience with earlier designs. Second, a performance-modeling tool provides a qualitative description of a circuits behavior. Alternatively, it can use a learning process to accurately model circuit performance. Finally, an analog testing tool uses a fuzzy-neuron classifier to detect and classify faults in analog circuits.

Analog design optimization: A case study

An analog design optimization procedure is based on simulated annealing is proposed. The new method takes into account the cost function gradient, performing like simulated annealing at high temperatures and like a steepest descendent method near the frozen condition. The proposed method avoids the excessively time-consuming final iterations characteristic of the conventional simulated annealing algorithm.<<ETX>>

Multi-carrier Receiver for Broadband Power Line Communications

This paper presents the design of a broadband power line communication (BPLC) receiver optimized for reduced hardware complexity. To this end, the Radio-Frequency (RF) stage uses a direct conversion architecture while some innovative solutions are used in the base-band signal processing, such as a new frequency offset synchronization scheme based on the frequency domain. Every part of the receiver has been optimized using a new non-commercial hardware-software co-simulation package named BROCOLI (Broadband Co-simulation Library) based on a set of hierarchical models, specially developed for this application. A prototype of the BPLC transceiver has been built and some experimental results are shown which validate the design process and the implemented solutions.

Design of an efficient CORDIC-based architecture for synchronization in OFDM

This paper presents a new architecture to estimate the time and frequency offsets required to synchronize packed-based orthogonal frequency division multiplexing (OFDM) modulation receivers. The proposed estimators, which operate in the frequency-domain, use CORDIC (coordinate rotation digital computer) processors to achieve an efficient hardware implementation which is simpler than other computational intensive estimators based on processing in the time-domain. The hardware saving is twofold: the proposed implementation does not require complex cells such as multipliers or dividers; and some cells already existing in OFDM receivers for pay-load demodulation are reused during the synchronization phase. In addition, this paper also shows how to optimize the CORDIC cells, in terms of number of iterations, to provide a given signal-to-noise ratio (SNR) due to approximation error, and proposes an error propagation model for the proposed synchronization architecture

Simplified Detection for DVB-NGH MIMO Decoders

Nowadays, communication systems need to satisfy very demanding constraints in order to cope with users new necessities. One of the most promising techniques to improve the system capacity is multiple input multiple output (MIMO). However, the use of MIMO implies a huge complexity increase in the detection process. In this paper, a method to reduce the aforementioned complexity is presented. Although the proposed method is analyzed for digital video broadcasting next generation for handhelds, its implementation is useful for any MIMO system that requires the computation of log likelihood ratios (LLRs), used by the low density parity check codes. The presented technique consists of applying a simplification when calculating the Euclidean distances needed by the LLRs. The simplification avoids almost all the multiplications, very area demanding when translated into hardware, and presents a performance loss under 0.1 dB.

Using broadband power line communications in non-conventional applications

Power Line Communication (PLC) is a mature technology with application to different fields such as automated meter reading or indoor data communication. However, PLC shows a high potential for other nonconventional fields, like communications in vehicles, where little has been reported. This paper presents experimental results obtained with two broadband PLC modems in two different vehicles. The channel capacity and the impulsive noise are analyzed, and a propel model is proposed which can be of interest to guide future deployment of PLC technology in this new application field.

Modeling Airfield Ground Lighting Systems for Narrowband Power-Line Communications

Airfield ground lighting (AGL) systems are responsible for providing visual reference to aircrafts in the airport neighborhood. In an AGL system, a large number of lamps are organized in serial circuits and connected to current regulators that supply energy to the lamps. Controlling and monitoring lamps (including detection and location of burnt-out lamps) are critical for cost-saving maintenance and operation of AGL systems. Power-line Communications (PLC) is an attractive technology to connect elements of the AGL, reusing the power distribution cable as a transmission medium. PLC technologies avoid the installation of new wires throughout the airport infrastructure. This paper proposes a new model for power-line communication links in AGL systems. Every element (isolation transformer, primary circuit cable, and lamps) has been analyzed in laboratory and modeled using SPICE. The resulting models have been integrated to build a complete power-line link model. Simulation results are compared to experimental results obtained in real conditions in the Airport of Seville (Spain).