Realization of Four-Terminal-Pair Capacitors as Reference Standards of Impedance at High Frequency Using Impedance-Matrix Method

Abstract

The four-terminal-pair air capacitors of nominal values 1000 and 100 pF have been realized as reference standards of impedance upto 10 MHz using impedance-matrix method. The reported work has been successfully practically implemented at the National Physical Laboratory India (NPLI) in the direction of establishing metrological traceability of capacitance standards at high frequency (HF). The realization procedure is based on the determination of effective capacitance of each capacitor as a function of frequency upto 10 MHz. It involves single-port-impedance measurements at HF using RF impedance analyzer and capacitance measurements at 1 kHz using ultraprecision capacitance bridge. The least squares data approximation method is thereafter used to extrapolate the resistive and inductive components of the measured HF single-port-impedances to lower frequencies down to 1 kHz. The measurement automation program has been developed to measure the single-port impedances at set of frequencies between 40 and 100 MHz using impedance analyzer. The air capacitors characterized using impedance-matrix will be used as reference standards of impedance at NPLI to calibrate impedance bridges, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCR</i> meters, and impedance analyzers upto 10 MHz.