Frequency-dependent dielectric permittivity from 0 to 1 GHz: Time domain reflectometry measurements compared with frequency domain network analyzer measurements

Measurements on a seven-wire coaxial probe carried out with a cable tester in the time domain are compared with measurements carried out with a network analyzer in the frequency domain. Results are compared in the frequency domain and in the time domain. The frequency domain results of the time domain measurements are less smooth than the direct frequency domain measurements, but similar trends can be observed. The measurements carried out with the cable tester (Tektronix 1502B) clearly have a frequency content well above 3 GHz for measurements in air but with a very low signal-to-noise ratio for the higher frequencies. The useful frequency band for measurements carried out with a seven-wire probe depends on the dielectric properties of the material being measured. The higher the complex dielectric permittivity, the lower the useful frequency band. Methods are presented for calibrating seven-wire coaxial probes and measuring the frequency-dependent dielectric properties of soil samples using a combination of frequency and time domain analyses. The approach does not depend on a choice of frequency bandwidth. A Debye relaxation curve is capable of describing the frequency domain dielectric permittivity of sandy soils containing a soil solution with an electrical conductivity of approximately 0.4 S m(-1). Results indicate an effective bandwidth of at least 0-1 GHz for sandy soils.