This document analyzes and designs a reconfigurable antenna for cognitive radio applications that can operate in both the 2400 MHz ISM band and 1850 MHz GSM band. A square spiral monopole microstrip antenna was designed using a 0.702 mm Rogers 3003 substrate. The antenna consists of a microstrip λ/4 feedline and λ/2 resonator. Analysis shows that a discrete inductor element is needed to reconfigure the antenna to operate at 1850 MHz. Simulations demonstrate the antenna achieves resonance frequency changes and maintains radiation patterns when the inductor value is varied. The designed antenna meets requirements for cognitive radio applications and offers reconfiguration without increasing physical length.