A radiometric heating/sensing probe for radiating electromagnetic waves of a first frequency capable of heating tissue and detecting electromagnetic waves of a second frequency emitted by the tissue indicating tissue temperature. The probe includes a dual frequency antenna, a signal transmitting path to the antenna and a signal receiving path from the antenna to a radiometer. A diplexer connected between those paths inside the probe includes a quarter wave stub in the form of a shorted slab line-type transmission line in the signal transmitting path. The entire probe package is only about 0.4 in. long and 0.08 in. in diameter so that it can be used in many minimally invasive applications.
