Measurements of short-pulse propagation through concrete walls

The authors recently performed a series of experimental measurements of transient electromagnetic (EM) propagation through two different concrete walls. Several different short-duration pulses were used for the incident radiation, with frequency content from VHF to 20 GHz. Both walls were 30 cm thick, with three internal layers of reinforcing steel bars. For this particular set of data, the incident wave polarization was vertical linear only. Corroborating swept-frequency measurements were made with a vector network analyzer. This paper describes the propagation measurements through the two walls, and the propagation model of a lossy dielectric layer. They also examine the transfer function, dielectric constant, loss tangent, attenuation constant, and time-domain impulse response of these walls. The attenuation increases steadily with frequency, and is a strong function of the moisture content of the concrete. The time-domain pulse attenuation and dispersion are consistent with the lowpass-filtering effect of this attenuation loss vs. frequency. The time domain behavior will be very useful in time-domain radar studies of ground-penetrating radar, free-space layered measurement systems, etc