A parametric study on the effects of the variations in line width on the circuit model parameters of a planar spiral inductor on GaAs

• Main Author: Abdelbagi, Selma
• Format: Thesis
• Language: English
• Published: 2009
• Online Access: http://utpedia.utp.edu.my/2917/1/MUSTAFA.pdf; http://utpedia.utp.edu.my/2917/

The increasing demands for low cost radio frequency integrated circuits (RFIC’s) has generated great attention in on-chip passive components. A spiral inductor is an important passive component for many radio frequency circuits such as low noise amplifiers, mixers, switches, and voltage controlled oscillators. Considerable effort has gone into the design and modeling of the spiral inductor, however, very little research has investigated the effects due to the errors introduced into the spiral inductor modeling. This research investigates the effects of variations in conductor line width on equivalent circuit model of planar rectangular spiral inductors. A parametric study is performed where a full wave electromagnetic simulator, Sonnet TM, is used to simulate several sets of inductors on Gallium Arsenide (GaAs) substrate having different dimensions. The scattering parameters of a particular inductor were simulated over the desired frequency range. These simulated scattering parameters are used to extract the equivalent circuit model parameters using optimization process. The extracted inductor model parameters are validated through the existing physics based formulae. the simulation results reveals that variations in the conductor line width affect every parameters in the equivalent circuit model of the inductor i.e. the series inductance, the series resistance, the capacitance between the inductor turns. Change in series inductance due to the variations in the conductor line width is nearly a linear function of the nominal inductance. Variation in series resistance is an exponential function of nominal conductor width. Change in line to line capacitance due to variations in conductor line width is an exponential function of nominal spacing between conductors. Finally, variations in conductor line width have no or little effects on substrate capacitance. Curve fitting techniques are utilized to extract simple equations useful for estimating the changes in the circuit model parameters with respect to the variation in conductor line width. These equations advantageous to the RFIC’s designer since the inductor equivalent circuit model parameters can easily be modified to account for variations in conductor line width and also they can be used during circuit design optimization to explore inductor space.