A low profile temperature transducer has a working surface for placement against a body surface and a first output. The transducer is a flat laminate composed of alternating conductive and dielectric layers. The laminate defines at least one slotline antenna for exposure to the body surface to pick up thermal emissions from the underlying tissue at depth. A feed network having a characteristic impedance is connected to the first output and a slotline-to-stripline transition is connected between the at least one antenna and the feed network, the transition providing a match between the impedance at the at least one antenna and the characteristic impedance. Also, a temperature sensor may be present at the working surface to detect the body surface temperature under the transducer, that surface temperature being used to calculate actual temperature at depth.