Measurements of AC Resistances up to 10 MHz Using a VNA and Calculable Adapters

Abstract

Resistors are widely used in industry for several applications, for example power measurements and electrical transient measurements. However, it is necessary to evaluate the amplitude and phase of the resistor impedance according to the frequency before their use. The existing low frequency methods used to calibrate resistors are limited to 1 MHz. A high frequency approach is proposed to characterize resistors up to a few MHz with traceable measurements. This method is based on a vector network analyzer (VNA). Type-N or BNC cables can be used to perform traceable measurements in the megahertz frequency range. However, several electrical resistors used in industry or in metrology laboratories are equipped with other types of connectors (such as UHF or BNC) that require adapters to establish the electrical connection with the VNA. In this article, an example of resistors with UHF connectors is presented to illustrate this case. Calculable RF adapters for UHF to Type-N connectors are developed to cancel the impact of these adapters on impedance measurements. The proposed method can be adapted for other type of connectors. Hence, the frequency response of resistors can be obtained in the megahertz frequency range. While the uncertainties are typically higher than those obtained with low frequency methods, the method presented in this paper is to our knowledge, the only one capable of simultaneously measuring the amplitude and phase of resistor impedance up to a few megahertz with acceptable uncertainties and traceability established to the International System of Units (SI).