The disclosure provides an electromagnetic (EM) sensor system and method that permits rapid and non-invasive measurement of blood glucose or other biological characteristics that exhibits a unique spectral signature, such as its complex electrical permittivity within the frequency range from near DC to microwave frequencies. Low-level EM signals are coupled through the skin and modified by electrical properties of the sub dermal tissues. These tissues essentially integrate with the sensor circuit as they interact with the transmitted EM energy. The guided-wave signal can be sampled and converted to a digital representation. The digital information can be processed and analyzed to determine the frequency-sensitive permittivity of the tissues and a determination of blood glucose level is made based upon the sensor output. The sensor design and method has wide-ranging applicability to a number of important measurement problems in industry, biology, medicine, and chemistry, among others.
