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Analysis and optimization of an RF baseband transimpedance amplifier with low-pass filter structure and positive feedback

Loos, Cisko (2017) Analysis and optimization of an RF baseband transimpedance amplifier with low-pass filter structure and positive feedback.

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Abstract:The goal of this assignment is to find ways to optimize the selectivity of a double-sided TIA filter for use in multiband transceivers. Its circuit features passive R and C components for attenuation and capacitive positive feedback to achieve high linearity. The analysis of the TIA filter is only in baseband and assumes ideal mixing. An equivalent circuit is derived, from which a system of equations is found. A general way of solving a system of equations with higher order solutions using MATLAB is found, and used to find expressions for the transfer function and input impedance of the TIA filter. These expressions are found to be correct by simulating their frequency response in Simulink and comparing them to circuit simulations in LTspice. Approximating the transfer function to a standard second order form proved to be appropriate in the relevant frequency range. System properties like natural frequency and quality factor are extracted from this approximation. Next, more insight is gained in the influence of some capacitors on the transfer function of the TIA filter by stepping their parameter values in simulation. These values are then tuned to achieve an f-3dB point at 9.7MHz, a maximum of +l.3dB overshoot and a roll-off of -44dB between lOMHz and lOOMHz, providing slightly more optimal selectivity while keeping the overshoot within acceptable range. This report provides a MATLAB implementation that has been proven to significantly ease the derivation of large equations. It can be used to automate much of the design and optimization process of higher order systems.
Item Type:Essay (Bachelor)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering BSc (56953)
Link to this item:http://purl.utwente.nl/essays/74929
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