Microwave permittivity of dry sand

The complex, relative dielectric permittivity epsilon of dry desert sand, collected at the Grand Erg Oriental in Ksar Ghilane, Tunisia, in October 1994, was measured with microwave resonators at frequencies between 0.245 and 6 GHz, The results are presented here, Whereas the real part epsilon' is nearly independent of frequency, a monotonous decrease of the imaginary part epsilon'' with increasing frequency is observed. The data can be fitted to a Debye relaxation spectrum with a relaxation frequency of about 0.27 GHz, leading to a nearly frequency-independent penetration depth of about 1 m over the range from 1-10 GHz, The spectrum can be explained by Maxwell-Wagner losses of semiconducting spheres embedded in a nonconducting sand medium.