FM-CW radar performance in a lossy layered medium

FM-CW radar is capable of detecting subsurface anomalies by using linear sw eep frequency transmission of a periodically repetitive continuous FM signa l. Due to the continuous-wave nature, the peak power of the FM-CW radar is usually in the range of hundreds of milliwatts. In cases where high resolut ion is necessary, the FM-CW radar is preferred because of the simple hardwa re structure and the availability of low-power components. The distance fro m the antenna to an anomaly can be determined by FM-CW radar in lossless me dia. In this paper, we present both analytical and numerical methods for mo delling FM-CW radar performance in lossless and lossy layered formations fo r 1D and 2D cases. The FM-CW operating frequency is set in the range of 1-2 GHz, and the sweep periods are 10 ms and 2 ms, respectively. An inversion formulation is discussed to invert the distance and dielectric constant sim ultaneously from the spectrum of the received signal by using FFT and the ' range equation'. The spatial resolution is about one-third of the center wa velength and the depth of penetration is about 4 m in a medium having a con ductivity less than 1 mS/m. The FM-CW radar technique cannot be used in a l ossy medium having conductivity more than 30 mS/m. The spectrum and images of multilayer formations is also studied. (C) 1999 Elsevier Science B.V. Al l rights reserved.