Design of CMOS front-end receiver for wideband optical communication systems.
Date of Issue2011
School of Electrical and Electronic Engineering
Centre for Integrated Circuits and Systems
In the current wireless indoor communication market, Bluetooth is the dominating technology used. The main purpose of Bluetooth is to eliminate the need of cables interconnecting electronic devices. Operates at a range of 10 meters with the top data rate of 24 Mpbs, the use of Bluetooth in terms of high speed data communication is however, limited. To achieve high data rate transmission, optical communication is the preferred method. In today’s high speed optical fiber communication systems, such as 10Gb/s Ethernet and SONET OC-192 / STM64, transimpedance amplifiers are widely utilized due to its performance of wide bandwidth as well as low noise level. Transimpedance amplifier, which translates and amplifies incoming current generated by photodiode into a voltage signal, is an import part of receiver frontend. In short distance applications like Local Area Network, unlike the stringent requirement of low transmission loss in long distance applications, cost effectiveness are of great importance due to the high deployment scale. As a result, integrated deep submicron CMOS solutions have been accepted as a suitable solution for short distance applications, due to its high manufacturability, low cost and acceptable performance. Thus, it is the interest of current research society to design transimpedance amplifier with better performance with low cost material and manufacturing technology. Wireless optical communication is more feasible for short range communication system due to high path attenuation, as such the requirement for a transimpedance amplifier with better performance as well as affordable material and manufacturing technology is desired. In this thesis, an indoor wireless optical communication system using white LED light as the communication channel has been proposed. In the proposed system, signal is carried with light wave transmitted by white LED. The receiver terminal consists of a photodiode and a general CMOS optical receiver front-end. The specific design requirements and techniques for CMOS transimpedance amplifiers in a fully integrated CMOS optical receiver for the proposed system are then discussed. A novel cross-coupled current conveyor based transimpedance circuit topology has been proposed based on the requirement and techniques presented. This proposed cross-coupled current conveyor based input stages is capable to present a “zero” input impedance so that a high bandwidth can be achieved. Some well known bandwidth enhancement techniques have also been implemented in the proposed design. The proposed transimpedance amplifier has been implemented using GlobalFoundries’ 0.18μm CMOS technology. The simulation as well as the measurement results have been presented, compared and analyzed in this thesis. The novel circuit also facilitates differential structure, while greatly reduce the cost and power consumption. The result indicates that the proposed TIA is indeed suitable to be employed in a low noise optical wireless communication system, however, further improvement of bandwidth, layout optimizations are necessary for a high speed system. Design challenges for limiting amplifier have also been reviewed in this thesis, and a DC generating circuit is proposed to be incorporated in the limiting amplifier design as DC offset compensation network, making the limiting amplifier to be fully integrated by eliminating the traditional off-chip component in the offset compensation network. The simulation result has been presented. In summary, the thesis focuses on CMOS design of transimpedance and limiting amplifiers which are major components of an optical receiver front-end. Following review of design challenges, a new transimpedance amplifier and a fully integrated limiting amplifier have been proposed and studied.
DRNTU::Engineering::Electrical and electronic engineering::Wireless communication systems