A microwave sensor assembly includes a signal generator for generating at least one microwave signal and an emitter coupled to the signal generator. The emitter is configured to generate an electromagnetic field from the at least one microwave signal, wherein the emitter is detuned when an object is positioned within the electromagnetic field such that a loading signal is generated. The microwave sensor assembly also includes a detector coupled to the emitter and to the signal generator. The detector is configured to calculate at least one of an amplitude, a phase, and a power of the loading signal at a primary frequency of the loading signal for use in measuring a proximity of an object to the emitter.