Microwave radiometry offers a means for noninvasive measurement of temperature that could be useful for diathermy/hyperthermia control since the relatively long wavelengths (compared to infrared) allow depth sensing. This promise has been frustrated by severe loss of signals from depth sites when lossy dielectric media are interposed between the thermal source and the radiometer. Thus, superficial thermal sources overwhelm the deeper sources. This limitation impedes radiometer application to diathermy/hyperthermia control. Especially as hyperthermia is a valuable adjunct to radiotherapy and chemotherapy in the treatment of cancer, these limitations may effect overall progress in the area. An alternative method to enhance radiometric sensibility to depth thermal sources is the use of multiple antennas with cross product processing to scan a zone common to two antennas. The cross product processing enhances sensibility of depth sources by peaking the system's response at various ranges. In addition, correlation radiometry enhances spatial and thermal resolution by the detection of thermal gradients. The correlation radiometer is especially suitable for use with a modified version of a previously developed dual waveguide, 918 MHz contact applicator. A diplexler may be used to separate the transmitter and receiver portions of equipment to provide real time control whereby the antennas serve both as sensors (for the correlation radiometer) and effectors (for the diathermy/hyperthermia).