Microwave permittivity of dry sand

The complex, relative dielectric permittivity ε 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 0.243 and 6 GHz. The results are presented. Whereas the real part ε\´ is nearly independent of frequency, a monotonous decrease of the imaginary part ε" 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