A sectored receiver for infrared wireless networks

This paper presents an experimental sectored receiver for infrared wireless networks. The receiver comprises two sectors, each with a switched gain front-end and a signal-to-noise ratio estimator. These are then interconnected with a best-sector selector unit, able to compensate the gain switching characteristics of the front-ends. The circuit has been designed in a 0.8 μm CMOS technology

Bandwidth aspects in second generation current conveyors

This paper discusses bandwidth problems associated with second-generation current conveyors (CCII). In particular, our work is centered in high-capacitance applications, and has been oriented for wireless optical links and applied physics. We discuss techniques for improving bandwidth in these CCIIs, and develop a new CCII structure with larger bandwidth than traditional circuits. These circuits are then compared in terms of their noise and dynamic range characteristics. A test circuit was developed to verify these different bandwidth behaviors

Design techniques for high performance optical wireless front-ends

Wireless optical networks usually have demanding specifications in terms of bandwidth, dynamic range and sensitivity. The front-end is a critical element for the fulfillment of these demands. This paper discusses several design aspects of front-ends for optical wireless communications, covering techniques for achieving high gains, high input dynamic ranges, improving noise performance, and reducing electromagnetic interference (EMI). The paper further presents some experimental results of many of the techniques here described. The cumulative usage of those techniques significantly increases system performance, in terms of sensitivity, power and bandwidth even with low cost, CMOS technologies

Medição de relação sinal ruído em receptores ópticos atmosféricos

Nesta dissertação discutem-se os problemas encontrados no projecto e implementação de um circuito capaz de efectuar a medição da relação sinal ruído em receptores ópticos, usando tecnologias de circuitos integrados CMOS. As várias estratégias estudadas para implementar a medição de relação sinal ruído possuem uma característica comum, são capazes de efectuar processamento analógico de sinais. Várias categorias foram investigadas, nomeadamente: circuitos de processamento em corrente, malhas translineares, multiplicadores de quatro quadrantes, divisores analógicos, amplificadores logarítmicos e current conveyors. É apresentado e descrito o sistema de referência para o qual foi desenvolvida uma unidade de medição de relação sinal ruído. Este sistema consiste num receptor óptico sectorizado com dois sectores de recepção e um sistema de selecção do tipo best sector. Cada um dos sectores de recepção compreende um amplificador de transimpedância de ganhos comutados e um medidor de relação sinal ruído, que processam o sinal e ruído gerados num fotodetector tipo PIN. Todo o sistema foi implementado num ASIC CMOS usando a tecnologia standard de 0.8μm da AMS. São ainda discutidos os resultados de simulação obtidos durante a fase de projecto do circuito, bem como os resultados obtidos em testes efectuados com o circuito real. No final tiram-se algumas conclusões e traçam-se algumas linhas de orientação para futuros desenvolvimentos do sistema. ABSTRACT: This thesis discusses the problems found during the project and implementation of a circuit capable of measuring the signal to noise ratio in optical receivers, using CMOS integrated circuit technologies. All the circuits that were investigated during the specification of this work have one common characteristic; they are capable of processing analogue signals in an analogue sense. Several circuit categories were investigated, namely: translinear loops, four quadrant multipliers, analogue dividers, logarithmic amplifiers, current conveyors and current processing circuits. The reference system designed to demonstrate correct operation of the signal to noise measurement circuit is presented and described. This system consists of an optical sectored receiver with two receiving sectors and a best sector selection unit. Each one of the receiving sectors comprises a switched gain transimpedance amplifier and a signal to noise measurement circuit, which are responsible for treatment of the signal and noise generated in a PIN fotodetector. This system was implemented in one CMOS ASIC using a standard 0.8μm technology from AMS. Simulated and measured results are presented and discussed. Some conclusions and future work guidelines are drawn at the end of this test