SYNTHETIC BANDWIDTH CORRELATION RADIOMETER FOR THE RESOLUTION IMPROVEMENT OF A THERMAL MICROSENSOR

We have conceived a distributed thermal sensor based on the processing of the correlation function of the thermal noise emitted by the two p orts of a small-size lossy transmission line in the microwave domain. The transducer is a lossy coplanar waveguide (LCPW) where losses are c reated by a thinning down of the central conductor. The two ports of t he LCPW are connected to a microwave correlation radiometer. The knowl edge of electrical characteristics of the LCPW and an original applica tion of the Kalman filtering to the signals recorded as a function of the delay time of the correlator allow us to retrieve the temperature profile along an LCPW of length 2 cm deposited on alumina. In the pres ent situation, doe to a bandwidth limited between 2 and 4 GHz, the spa tial resolution of temperature retrieval is about 4 mm. We show in thi s paper that title application of this processing to the radiometric d ata obatined with foru radiometers of bandwidth 2 GHz. working at 3, 3 5, 64 and 91 GHz, the spatial resolution, with an LCPW of length 1 mm becomes 200 mu m. These interesting results lead to the definition of a synthetic bandwidth correlation radiometer, and to a demonstration o f the feasibility of a new thermometric microsensor. (C) 1998 John Wil ey & Sons, Inc.