Systems and methods are provided for characterizing biological tissues through their thermal signatures that include directing microwave energy into a biological tissue using a first slot antenna, detecting microwave radiation emitted by the biological tissue using a second slot antenna, generating output signals corresponding to the microwave radiation, processing the output signals to characterize a temperature of the biological tissue as a function of time to yield temperature characteristics, and characterizing a biological function of the biological tissue based on the temperature characteristics. The first and second slot antennas can be defined using a dual mode antenna and the generating can include alternatively collecting signals from the second slot antenna through a first low noise amplifier (LNA) and a reference load through a second LNA that the two LNAs are substantially identical.