Nonlinear System
A.R. Ghomi Taheri; F. Setoudeh; M. B. Tavakoli
Abstract
Background and Objectives: The Differential transform method (DTM) is used in the analysis of ordinary, partial, and high-order differential equations. Recently, the DTM is used in the nonlinear analysis of physical nonlinear dynamic systems.Methods: The DTM method is used to analyze and analytically ...
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Background and Objectives: The Differential transform method (DTM) is used in the analysis of ordinary, partial, and high-order differential equations. Recently, the DTM is used in the nonlinear analysis of physical nonlinear dynamic systems.Methods: The DTM method is used to analyze and analytically solve the nonlinear mathematical model of bias current-controlled Colpitts oscillator with variable coefficients. Intervals of the validity of the proposed method are evaluated by using the fourth order Runge-Kutta method (RK4M). In this note, the Lyapunov exponent (LE) can be used to analyze the Colpitts oscillator. By using DTM, the LEs are calculated analytically with unknown parameters in a short interval of time t[0, 3 Sec]. Results: In this paper, intervals of the validity of the proposed method are evaluated using RK4M. In addition, LEs are calculated using analytical and numerical methods based on DTM technique and Wolf method, respectively. LEs of the proposed system are presented as a function of the control parameter to confirm the applied technique’s usefulness. Conclusion: By comparing these two methods, the proposed DTM analytical technique is relatively more precise. Simulation results confirmed the impact of different parameters on LEs with two different initial conditions. The results show good accuracy of the DTM in short time intervals t[0, 3 Sec].
Power Divider
M. Mirzajani Darestani; M. Tavakoli; P. Amiri
Abstract
Background and Objectives: In this paper, a new design strategy was proposed in order to enhance bandwidth and efficiency of power amplifier.Methods: To realize the introduced design strategy, a power amplifier was designed using TSMC CMOS 0.18um technology for operating in the Ka band, i.e. the frequency ...
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Background and Objectives: In this paper, a new design strategy was proposed in order to enhance bandwidth and efficiency of power amplifier.Methods: To realize the introduced design strategy, a power amplifier was designed using TSMC CMOS 0.18um technology for operating in the Ka band, i.e. the frequency range of 26.5-40GHz. To design the power amplifier, first a power divider (PD) with a very wide bandwidth, i.e. 1-40GHz, was designed to cover the whole Ka band. The designed Doherty power amplifier consisted of two different amplification paths called main and auxiliary. To amplify the signal in each of the two pathways, a cascade distributed power amplifier was used. The main reason for combining the distributed structure and cascade structure was to increase the gain and linearity of the power amplifier.Results: Measurements results for designed power divider are in good agreement with simulations results. The simulation results for the introduced structure of power amplifier indicated that the gain of proposed power amplifier at the frequency of 26-35GHz was more than 30dB. The diagram of return loss at the input and output of power amplifier in the whole Ka band was less than -8dB. The maximum Power Added Efficiency (PAE) of the designed power amplifier was 80%. The output p 1dB of the introduced structure was 36dB, and the output power of power amplifier was 36dBm. Finally, the IP3 value of power amplifier was about 17dB.Conclusion: The strategy presented in this paper is based on usage of Doherty and distributed structures and a new wideband power divider to benefit from their advantages simultaneously.
