It is well known that quad-ridged horn antennas in general have impedance and radiation characteristics that are significantly worse than that of their double-ridged counterparts. Normally a voltage standing wave ratio (VSWR) of 3 over the operational bandwidth is used for the design specification of quad-ridged horn antennas. The bandwidth of operation is severely restricted due to the excitation of higher order modes in the co-axial to waveguide transition of the antenna. The higher order modes cause a break-up in the radiation pattern of the antenna and large dips in the boresight gain. The performance of the quad-ridged horn antenna with pyramidal sidewalls is improved by separating the antenna into the transition and flared horn sections, and optimizing these sections individually. It is shown that a transition section with a pyramidal cavity and steps, and a flared horn section with an exponential profile with a circular segment for the ridges deliver the best performance. These configurations for the transition and flared horn sections are combined in the complete antenna. The optimized antenna has a 12.5:1 operational bandwidth with improved performance in terms of the VSWR, the coupling between the ports and the boresight gain. A prototype of this antenna is manufactured. Good agreement between the measured and simulated performance is achieved. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / unrestricted