Design of a Self-Calibrating Wide-Band Radiometer

Using radiometers is an established method for non-invasive temperature measurement of weakly conducting objects like biological tissue. Therefore, self-calibrating radiometers using reference noise sources and circulators are established if only a small measurement bandwidth is required. This work proposes a self-calibrating wide-band radiometer, allowing the use in further applications like temperature measurement of objects in closed cavities. Different combinations of reference noise sources, reference impedances, ground connections and capacitances are used to calibrate the system. The complex values of the reflection parameter of the sensor are obtained using a mathematical algorithm. Therefore, parallel capacitances are added to the signal path. With a known reflection factor, the inherent system noise can be eliminated when determining the absolute temperature. This allows the use of directional couplers and measurement in a wide frequency range with simple electronics.