Radio sources with a gigahertz-peaked spectrum (GPS) are thought to be the progenitors of large-scale radio galaxies, with the youngest sources having spectral peaks at the highest frequencies. These young radio galaxies are under-represented in current radio surveys as their peak emission is at frequencies higher than those of the surveys. The declining density of radio sources seen at higher frequencies means that large areas of sky are needed to capture statistically significant numbers of these sources. However, large-area surveys at high frequencies have until now been prohibitive in their required observing time. A recent survey using the Australia Telescope Compact Array, and a custom-built Wide Band Analog Correlator has drastically reduced the required observing time and made it possible to conduct a high-frequency radio survey that covers the entire southern sky -- the Australia Telescope 20GHz Survey (AT20G). The AT20G provides spectral information at 5, 8, and 20GHz for ~4000 sources, and is thus an rich source of potential young radio galaxies. In this thesis I describe the development and implementation of the AT20G hardware, the observational techniques, and the calibration and data reduction process for the AT20G survey scanning observations. I describe and present a catalog of sources from the AT20G scanning survey which complements and extends the AT20G follow up source catalog of Murphy et al. (2010). This thesis also describes the identification and investigation of peaked-spectrum radio sources, with particular interest in the high frequency GPS population with spectral peaks above 5GHz.

Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Physics, Faculty of Science.