Passive resonators have been used for materials characterization, and in many different sensing applications. The passive resonator approach utilizes the frequency shift of the resonator due to the change in the material's dielectric property. Passive resonators, however, suffer from the effects of low-quality factor, and thus they do not provide high sensitivity to small changes in material parameters. In this thesis, an active resonator for real-time material sensing for bio-media applications is presented. The resonator presented provides a high-quality factor based on a passive planar resonator built with an active feedback loop to dramatically increase the resonator's quality factor. The designed resonator operates at 1.5 GHz and provides a quality factor of 40,000. This is an improvement of about 50 times over that of a passive resonator. Changes in the permittivity of a material were measured by placing the material in the resonator's gap capacitor region, and therefore changing the resonance frequency of the resonator. It is demonstrated that this resonator can detect different material permittivity with nanoliter sample amounts. The active resonator is able to detect liquid permittivity changes up to 1.5% IPA concentration difference.