Doris Csipkes

An OTA-C field programmable analog array for multi-mode filtering applications

This paper presents a reconfigurable analog array and its possible application in multi mode wireless communication equipments. The array is built around configurable analog blocks comprised of linearized, fully differential transconductance amplifiers. The circuit sacrifices a degree of generality in favor of specialized filtering operations at high frequencies, low consumption and good linearity, all required in modern communication devices. The programming of the filter frequency parameters is achieved through binary weighted transconductor arrays and a capacitance scaling circuit. The proposed analog array has been simulated at transistor level by using the Eldo simulation engine on a 90nm digital CMOS process.

On the Design of a Reconfigurable OTA-C Filter for Software Radio

This paper presents a novel approach in the design of integrated reconfigurable and programmable analog filters for commercial mobile applications. The method is described in the specific context of an analog filter which is capable of operating in both the complex and real domains; the filter is designed using the OTA-C technique, features a programmable order and transfer function and is envisioned as part of a combined low- IF/zero-IF receiver architecture for a software defined radio transceiver. The novel method is demonstrated by presenting the simulation results of the real low- pass/complex band-pass filter for a 0.5 dB Chebyshev approximation.

A Reconfigurable and Programmable Filter for Software Defined Radio Based on a Transconductor-Capacitor Analog Array

This paper presents a reconfigurable and programmable analog array intended to support the implementation of the filter stage in a software defined radio (SDR) wireless transceiver. The analog array is designed using the transconductor-capacitor (Gm-C) technique and may implement a wide variety of analog filters of programmable order and transfer function. The filtering stage implemented by the analog array is envisioned as part of a combined low-IF/zero-IF receiver architecture for an SDR transceiver. A modular method of synthesizing various order state-variable filters is used as tool for demonstrating the capabilities of the analog array. Different filters have been modeled, in both the complex and real domains, to demonstrate the capability of the analog array.

An evolutionary approach to design and calibration of reconfigurable OTA-C filters

Latest trends in communication and consumer electronics target the development of fully adaptive systems on mixed signal systems-on-chip. This paper proposes an evolutionary approach to adaptive filter design. The hardware support of the evolutionary design algorithm is a field programmable analog array (FPAA). The FPAA has been implemented with OTA-C techniques. The synthesis algorithm has been developed considering the particularities of the proposed FPAA and of the supported filter structures. Topological reconfiguration is performed with a lookup table, parametric design is performed with evolutionary computation methods and wide-band self-calibration is achieved by means of a phase locked loop. The filter sizing algorithm is suitable for both intrinsic or extrinsic evolution and has the potential to be hard-wired in dedicated digital circuitry. Extensive transistor level simulations performed on the evolved adaptive filters prove the functionality of the proposed software and the underlying circuitry.

A variable topology analog filter suitable for multi-mode wireless applications

A reconfigurable channel or band-select filter is one of the key elements of multi-mode analog front ends. This paper presents the system level aspects of a fully reconfigurable analog filter. The proposed circuit is based on analog array-like architecture that enables the mapping of low pass and polyphase band pass filters on a regular structure of reconfigurable unit elements. The current conveyor based topology represents a compromise between the generality of traditional field programmable analog arrays and the highly specialized requirements imposed by multi-mode wireless receiver architectures.

Machine vision applied to highly variable objects

The work presented in this paper addresses Machine Vision (MV) applications to objects of ill defined shape, size, colour or texture. Development of Machine Vision through the years from its origin in the 1950s to date is analysed and their progress and trends are discussed. The paper concentrate in the small number of MV applications to object of high variability, it discusses and present solutions to main problems associated with the MV application to this type of objects. The problem of autofocus and problems associated with changes in illumination are discussed in details and solutions presented. The paper present and discuss general software architecture for MV applications. Two examples of this type of applications are presented: detection of microorganism in water and detection of suspicious activity in humans.

A generalized approach to complex filter design with open loop active cells

This paper describes a generalized approach to complex polyphase filter designs based on open loop active elements such as operational transconductance amplifiers or current conveyors. The low pass to band pass linear frequency transformation is performed on capacitors at circuit level, allowing a high degree of generality regardless of the employed synthesis method, voltage or current mode operation and the type of the fundamental open-loop building block. The equations and the corresponding implementations are determined for grounded and for floating capacitors, identified as the two connections typically used in high frequency integrated filters. The presented circuits support all-pole approximations and arbitrary transmission zeros of any order.

A Digitally Reconfigurable Low Pass Filter for Multi-mode Direct Conversion Receivers

This paper presents a novel approach to the design of integrated reconfigurable and programmable analog filters for commercial mobile applications. The method is described in the specific context of an analog filter, dedicated to multi-mode receiver front ends employing direct frequency conversion. The filter has been designed using state variables and leap-frog OTA-C techniques, features programmable order, digitally variable frequency parameters and wide linear range, while supporting several standard approximations. The fundamental OTA cell has been implemented with fully balanced second generation current conveyors, suitable for low voltage operation. The novel method is demonstrated by presenting the simulation results of the filter, designed for a 0.18 μm CMOS technology.

On the design of a reconfigurable OTA-C filter for software radio

This paper presents a novel approach to the design of integrated reconfigurable and programmable analog filters for commercial mobile applications. The method is described in the specific context of an analog filter which is capable of operating in both the complex and real domains; the filter is designed using the OTA-C technique, features a programmable order and transfer function and is envisioned as part of a combined low-IF/zero-IF receiver architecture for a software defined radio transceiver. The novel method is demonstrated by presenting the simulation results of the real low-pass/complex band-pass filter for a 0.5~dB Chebyshev approximation.