A microwave biosensor, suitable for the detection of dielectric overlays, formed by bonding of bio-molecules to a functionalized
substrate, is investigated. The sensor consists of a resonant coupled split-ring configuration in microstrip technology. An analytical
model for the sensor structure is developed and compared to measurement results. The complexity of the model is further reduced
and equations for resonance frequency shift and Q-factor change are determined from which the sensitivity and the detection limit
can be estimated. It is found that higher operating frequencies facilitate higher sensitivity and that the electrical conductivity of the
sample dominates the Q-factors and therefore the achievable accuracy.