The metrology of electrical impedance at high frequency: a review

The measurement of electrical impedance in the high-frequency range (loosely speaking, from 100 kHz to 100 MHz) is a common characterization technique in research and applications concerning condensed matter physics, engineering and biology. Commercial instruments for impedance measurement have specifications, including frequency range and base accuracy, continuously improving. The calibration of impedance instruments and standards in the high-frequency range represents a tough challenge for metrology laboratories; measurement methods and traceability paths are not as firmly established as those employed for lower (audio) or higher (microwave) frequencies. In the last few years, the problem has received increased attention from the metrology community. The paper gives a review of recent results in the field. (topical review)