A RGC-based,low-power,CMOS transimpedance amplifier for 10Gb/s optical receivers

ABSTRACT

In this paper, a new low-power transimpedance amplifier (TIA) based on a modified Regulated Cascode (RGC) circuit structure followed by a closed-loop post-amplifier is proposed for 10 Gb/s applications. The main objective of this work is to reduce the power consumption while, the frequency bandwidth of the proposed amplifier is increased considerably. The booster of a conventional RGC is modified by a cascoded transistor and its effect on the performance of the circuit is studied mathematically, which are verified by simulations. The bandwidth extension is occurred due to increasing the gain of the booster amplifier in the RGC stage, which isolates further the input capacitance and results in a reduced input resistance value hence, a higher input pole frequency is obtained in comparison with other conventional RGC structures. On the other hand, by using an active inductive peaking technique, the frequency of the output pole is also increased which results in a further extension of the frequency bandwidth for the proposed circuit. The proposed TIA is simulated using 90 nm CMOS technology parameters, which shows a 50.5 dBΩ transimpedance gain, 7.3 GHz frequency bandwidth and 1.22 µA_rms input referred noise value for only 1 mW of power consumption at 1.2 V supply voltage.     

Fabrication of metallic nanostructures of sub-20 nm with an optimized process of E-beam lithography and lift-off

A process consisting of e-beam lithography and lift-off was optimized to fabricate metallic nanostructures. This optimized process successfully produced gold and aluminum nanostructures with features size less than 20 nm. These structures range from simple parallel lines to complex photonic structures. Optical properties of gold split ring resonators (SRRs) were characterized with Raman spectroscopy. Surface-Enhanced Raman Scattering (SERS) on SRRs was observed with 4-mercaptopyridine (4-MPy) as molecular probe and greatly enhanced Raman scattering was observed.     

Time-domain analysis of lossy active transmission lines using FDTD method

In this paper, an accurate and efficient method for analysis of a GaAs MESFET including frequency-dependent losses of the electrodes in the time domain is presented. The time domain analysis is obtained based on the fully distributed model using finite-difference time-domain (FDTD) technique, with the assumption of the skin effect losses. The time-domain results are verified using the conventional time-domain to frequency-domain (TDFD) solution technique.     

A Lyapunov theory based UPFC controller for power flow control

Unified power flow controller (UPFC) is the most comprehensive multivariable device among the FACTS controllers. Capability of power flow control is the most important responsibility of UPFC. According to high importance of power flow control in transmission lines, the proper controller should be robust against uncertainty and disturbance and also have suitable settling time. For this purpose, a new controller is designed based on the Lyapunov theory and its stability is also evaluated. The Main goal of this paper is to design a controller which enables a power system to track reference signals precisely and to be robust in the presence of uncertainty of system parameters and disturbances. The performance of the proposed controller is simulated on a two bus test system and compared with a conventional PI controller. The simulation results show the power and accuracy of the proposed controller.     

A study on the effect of compressive strain on the resonance frequency of rectangular textile patch antenna: elastic and isotropic model

Textile antennas endure a lot of deformations like as compression during wearing that lead to change their characteristics. In the present paper, attempts have been made to investigate the effect of compressive strain on the resonance frequency of wearable rectangular patch antenna. The wearable antenna was produced using pure copper polyester taffeta fabric which is utilized in patch and ground parts. Also polyester needle-punched nonwoven fabric is used as a substrate material. Regardless the thickness of patch and ground, compression stress mainly changes the dimensions of substrate, resulting in a shift in the antenna resonance frequency. The relationship between applied strains and resonance frequency shift was derived analytically, experimentally, and numerically via finite element analysis. In addition, the mechanical properties of the substrate were also considered. In the analytical model and simulations, the substrate was assumed as an elastic and isotropic material. The results show a good agreement between analytical predictions, full wave simulations, and experimental measurements.     

Harmonic indices assessment by Wavelet Transform

In this paper, Total Harmonic Distortion (THD) and K-Factor based on Discrete Wavelet Transform (DWT) are inspected. A flexible THD based on DWT is proposed and the way of using Wavelet Transform, sampling frequency, suitable wavelet functions, and time interval to assess the signal are investigated. In addition, the effects of harmonics order, phase degrees, and transient on the indices are shown. The DWT-based indices are used to study some real waveforms and their advantages over Fast Fourier Transform (FFT) based indices are presented.As a case study, some of the system indices are utilized to compare the values of DWT with FFT indices in a typical distribution network in Tehran. In addition to the common system indices for this purpose, some new system indices based on K-Factor are proposed. At the end, the diversity of the DWT and FFT indices values are depicted.     

Characterizations of strontium(II) and barium(II) adsorption from aqueous solutions using dolomite powder

In this research, adsorption technique was applied for strontium and barium removal from aqueous solution using dolomite powder. The process has been investigated as a function of pH, contact time, temperature and adsorbate concentration. The experimental data was analyzed using equilibrium isotherm, kinetic and thermodynamic models. The isotherm data was well described by Langmuir isotherm model. The maximum adsorption capacity was found to be 1.172 and 3.958 mg/g for Sr(II) and Ba(II) from the Langmuir isotherm model at 293 K, respectively. The kinetic data was tested using first and pseudo-second order models. The results indicated that adsorption fitted well with the pseudo-second order kinetic model. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also determined using the equilibrium constant value obtained at different temperatures. The results showed that the adsorption for both ions was feasible and exothermic.