Effect of network analyzer trace noise on dielectric measurements with an open-ended coaxial probe

Accurate knowledge of material dielectric properties is fundamental for numerous applications, varying from the characterization of manufactured electrical components to the development of numerical human models, and the design of novel electromagnetic medical devices. Material dielectric properties in the microwave frequency range are generally measured with an open-ended coaxial probe connected to a network analyzer (NA). Although the calibration of the dielectric measurement system has been standardized, there are numerous sources of errors that can compromise the quality of dielectric measurements, such as imprecise measurement calibration, NA drift, system perturbation, and NA internal trace noise. The internal trace noise of NA is generally estimated by repeated measurements on the same material under the same condition. Alternatively, in this work, the internal trace noise of the NA has been taken from the NA datasheet and directly translated into permittivity random error and compared with the measured permittivity random error. Comparison between the two methods suggests the use of low intermediate frequency bandwidth in order to reduce dielectric measurement errors due to trace noise of NA.